I founded 4xxi in 2008, and since then I have been on the ‘agency’ side of this question. I have also been on the other side: I advise companies as a fractional CTO, and we audit AI systems that other teams built. The question I hear most often before a project is not ‘how do we build it?’ but ‘who should build it?’. An independent consultant, an agency, one of the Big 4, a fractional CTO, or simply our own AI engineer?
Short answer: choose by what you are missing: advice, hands, or both. For a decision, take an independent AI consultant, a freelancer or a fractional CTO (about $10–25k a month on the market for 20–40 hours). For a well-specified build, take an AI agency. For a multi-country programme where the risk is organisational, pay the Big 4 premium ($250–600+ per hour, more for partners). If AI will be full-time work for years, hire an in-house AI engineer. A small senior team such as 4xxi ($200 per hour) fits when you need advice and hands together.
Below is the longer answer to ‘AI consultant vs agency’, and to the four other options, with market rates I checked in October 2026. We are one of the options in this list, so I tried to be fair to the others, and there is a section on when you should not hire us.
Do you need advice, hands, or both?
Usually only one of them is missing, and most wrong choices I have seen come from mixing them up: a company buys advice when it needs hands, or buys hands when nobody has decided what to build. Therefore, before comparing vendors, it’s worth to write down which of three things you are actually missing.
- A decision. Where does AI pay off in our product or operations, and where not? Build or buy? Which model, and can we run it ourselves? (I compared commercial and open-source models in a peer-reviewed benchmark.)
- Delivery. Somebody who writes the code, integrates it with your systems and deploys it into your infrastructure.
- Measurement. This one is specific to AI. Somebody must check that the system is right often enough before launch, and that it stays right after the next model update. Traditional software either works or throws an error. An LLM feature can be wrong politely, with a confident tone, for months; how we measure that is in how to build an AI assistant that doesn’t hallucinate.
The options below differ mostly in which of these three they cover well.
AI consultant vs agency vs the rest: how do they compare on cost, speed and accountability?
On price, an independent AI consultant charges $75–350 an hour, a Big 4 firm $250–600+ an hour and a fractional CTO $10–25k a month, while agencies quote per build, from about €30k to over £1m. The bigger difference is who does the work and what they answer for. The table puts all six options side by side; market prices are as of October 2026, and the sources are listed right under it.
| Option | Market price (as of Oct 2026) | Who does the work | Speed to something working | What they answer for | Best for |
|---|---|---|---|---|---|
| Independent consultant or freelancer | $75–350/h; £500–2,000/day in the UK | The person you hired | Starts fast; capacity of one person | Advice, sometimes a narrow build | A decision, a review, a second opinion |
| AI agency or development studio | Builds of €30–150k in the Netherlands; UK custom AI builds £50k–£1m+ over 3–12 months | A delivery team; seniority varies | Weeks to months | Delivery against a spec | A clear spec and a fixed scope |
| Big 4 or large integrator | $250–600+/h, partners $1,000+; £2,000–5,000/day; readiness audits £50k+ | Large mixed team, partners on top | Months | Process, governance, programme | Enterprise programmes, regulators, change management |
| Fractional CTO or AI advisor | $10–25k/month for 20–40 hours; €8–15k/month in the Netherlands | One senior person, part-time | Decisions in days; no extra hands by default | Direction and decisions | Strategy, hiring, vendor choice |
| Your own AI engineer | UK median salary £87,500; US median ML engineer total comp $283,000 | Your employee | Months to hire, then fast | Fully yours | Years of sustained AI work, with a lead in place |
| Small senior team (where 4xxi sits) | Boutique range $125–350/h (up to $500 at the top); 4xxi charges $200/h | The engineers you meet | A prototype in days | Advice and delivery, measured | Advice plus hands, alongside your team |
Sources for the market figures: hourly ranges from Groovyweb’s AI consulting rates guide (updated 23 October 2026, aggregating Layer3 Labs, AY Automate and Alice Labs); UK day rates and project ranges from We Call Shotgun (August 2026); fractional CTO retainers from Pangea and First AI Movers (April 2026), which also gives the €30–150k agency build range; salaries from ITJobsWatch (UK permanent vacancies, 6 months to 28 October 2026) and Levels.fyi (US, updated 28 October 2026). The ranges are wide because the market is. Treat them as orientation, not as quotes.
When is an independent AI consultant or freelancer the right choice?
When you need one well-defined thing from one strong person: a decision, a second opinion on an architecture, a review of a vendor proposal, or a narrow build. Independent rates run from $75 to $350 per hour, and from £500 to £2,000 per day in the UK, according to the sources above.
The best independents are among the best people in the field. Some of the most useful public writing on LLM evaluation comes from independent practitioners (for example, Hamel Husain), not from companies. You talk directly to the person who thinks about your problem, and you do not pay for overhead.
However, there are two limits. Firstly, capacity: one person gets ill, goes on holiday, or takes a bigger client, and your project stops. Secondly, the title ‘AI consultant’ is not protected. Some people who use it today came from marketing or corporate training, which is fine for adoption workshops and not fine for a system that must answer correctly from your documents. Ask to see something the person built that is in production now, and ask how they measured it.
When does an AI agency or development studio make sense?
When the scope is clear and you want it delivered against a spec, with more than one pair of hands. Agency builds sit at €30–150k in the First AI Movers comparison for Dutch SMEs, and We Call Shotgun puts UK custom AI builds at £50k to over £1m, over 3–12 months.
An agency gives you capacity, a process and, often, a fixed price. That is a real advantage over a freelancer. The usual problem is the sales layer: the senior people at the pitch are not always the people who write the code, and the incentive of a large delivery team is billable hours.
For AI work there is one more question: who measures quality? In my practice, a lot of agency-built AI works perfectly in the meeting room and nobody knows how it behaves on real traffic. When we audit AI systems that other teams built, we look at security, robustness, the technology choices, automation and running costs. The problems repeat. Security and architecture come first. Then a ‘zoo’ of stacks that nobody can maintain. Then automation that is already available (on GitHub and similar platforms) but nobody switched on. I describe the checklist in how we audit an existing AI system.
Is a Big 4 firm or large integrator worth the premium?
Sometimes yes: when the main risk is organisational, not technical. Big 4 firms (Deloitte, PwC, EY and KPMG) and large integrators such as Accenture charge roughly $250–600+ per hour, with senior MBB and Big Four rates reaching $1,000+, or £2,000–5,000 per day in the UK. Their versions of an AI readiness audit start at £50,000, while the general UK range for the same kind of audit is £3,500–15,000 (both figures from We Call Shotgun).
What does the premium buy? Governance, regulatory experience across many countries, change management for thousands of employees, and a brand that a board and a regulator accept without questions. If you are a bank rolling out AI across many business units, these things are worth money.
If your problem is ‘we need an assistant that answers from our own documents and cites them’, you do not need a programme with a partner, three managers and a pyramid of analysts. One might argue that the big name reduces risk. For a scoped engineering problem I think the opposite is true: the more layers between you and the person writing the code, the more gets lost.
Is a fractional CTO a good option for an AI project?
Yes, if the hard part is deciding, and somebody else will do the building. Market retainers run at $10–25k per month for 20–40 hours, and $2.5–10k for a lighter 5–20 hours (Pangea’s retainer table; it lists AI and security specialists at $400–600 per hour), or €8–15k per month in the Netherlands (First AI Movers).
A good fractional CTO resolves exactly the questions that are expensive to get wrong: build or buy, which model and where it runs, whom to hire first, which vendor proposal is realistic and which one is a slide deck. She also says ‘no’ when AI is the wrong tool, which an agency rarely does.
The weakness is the same as with any single advisor: no hands. Advice without delivery often stays in a document. Moreover, a fractional CTO who cannot read the code will have a hard time judging whether the team is doing what it says.
I work as a fractional CTO and AI advisor myself, at the same $200 per hour we charge for everything else. For example, eight hours a week is about 35 hours a month, or roughly $7,000. A monthly retainer is also possible; we agree it with each client, and long or large engagements get better terms. The difference from a solo advisor is that when a decision needs code, there is a team behind me that typically starts within 3 business days of signing.
Should you hire an in-house AI engineer instead of a consultancy?
Hire when AI is going to be full-time work for years and you already have someone who can lead it. The median UK salary for an AI engineer in permanent vacancies was £87,500 in the 6 months to 28 October 2026, up from £77,500 for the same period a year earlier (ITJobsWatch). In the US, the median total compensation of a machine learning engineer is $283,000 (Levels.fyi, October 2026).
Let us do the arithmetic for the US case. $283,000 divided by $200 per hour is about 1,415 hours a year, which is roughly 70 per cent of one full-time person. And that is before recruiting fees, employer taxes, benefits and the months the seat stays empty. In the UK salaries are lower, so the break-even comes at fewer hours. Thus, if you need AI work for six months, or less than about 70 per cent of a full-time person, renting is cheaper. If you need a full person for three years, hire.
There is one trap. The riskiest setup I see is a single AI hire without a senior lead: nobody reviews her work, nobody can tell a good evaluation from a bad one, and when she leaves, the knowledge leaves too. A common working combination is to hire, and have an external senior team set up the architecture, the evaluation and the deployment pipeline together with your engineers. I describe how that works in working alongside your in-house team.
Where does a small senior team fit, and where doesn’t it?
A small senior team such as 4xxi fits when you need advice and hands at the same time, and you want the people who advise to be the people who build. This is where we sit, so read this section with that in mind.
What it looks like with us: senior engineers with 15–20 years each, no juniors and no sales layer, and I work on the projects myself. One rate, $200 per hour, for development, consulting and fractional CTO work alike. Two fixed-price entry points: a two-week AI opportunity audit for $5–10k, and a prototype sprint for $20k that produces a deployable prototype on your data in 5 business days (an evaluation set can be part of it; we agree the scope per project). The code, prompts and evaluation sets we build for you belong to you. Our own product, Edtek, is licensed non-exclusively; its chatbot answers from a publisher’s own content and cites the page.
Why can $200 per hour cost less than a cheaper studio? Because the total is rate times hours, and AI-assisted senior delivery needs fewer hours. We build our own products from idea to release in a few days, and we use the same pipeline for client prototypes. The cost side is covered in how much custom AI development costs.
How long does such an engagement last? From a few days to no fixed end date. With a legal publisher, three of us are on a plan of about 6–8 months, working side by side with their developers and devops (the details are in how we work inside an in-house team). For a payment company, the work is ongoing, with no end date: complex development, AI included. And sometimes a project takes a few days, because all that is needed is to deploy something correctly.
Our team feels that 4xxi is incredibly responsive, dedicated and smart. When something is not clear, they ask the right questions.”
Where it doesn’t fit: a small team cannot put dozens of people on a programme next month, and our hourly rate is higher than what many studios publish. If either of these matters most to you, read the next section.
When should you not hire us?
Don’t hire 4xxi in five cases: you need dozens of people at once; the work is a fixed non-AI spec where the lowest rate wins; you need adoption training rather than engineering; AI is a permanent full-time job and you already have a lead; or an off-the-shelf tool already does it. I’d rather say it here than discover it in week three of a project.
- You need dozens of people at once. A multi-country programme with procurement, change management and a regulator watching is Big 4 or large integrator territory. We are not built for that, and pretending otherwise would hurt you.
- The spec is fixed, the work is not AI, and the lowest hourly rate wins. If the task is well understood and nobody needs to make judgement calls, a cheaper studio will do it fine.
- You need adoption training, not engineering. If the goal is to teach your staff to use the AI tools you already bought, an adoption consultancy is the better match.
- AI is a full-time job for years and you have a lead. Hire. We can help set things up, but the long-term owner should be your employee.
- An off-the-shelf tool already does it. Buy it. And if the job is a simple workflow, your operations person can probably build it in n8n without anybody’s help.
Can you combine a fractional CTO, an agency and your own hire?
Yes, and a combination often works better than any single option. Three combinations work well. A fractional CTO or an independent consultant decides what to build, and then checks the agency’s work against that decision. You hire an in-house AI engineer, and an external senior team sets up the architecture, the evaluation and the deployment pipeline together with her. Or a short audit comes first, and its conclusion tells you which of the six options to buy next. The combination I would avoid is two advisors and no builder: you get two documents and no system.
How do you choose in practice?
Ask every option the same five questions, and compare the answers rather than the slides.
- Who exactly writes the code, and will I meet them before signing?
- Who owns the code, prompts and evaluation sets at the end of the project?
- How will you measure that it works, before launch and after the next model update?
- What happens if the first two weeks show it is not worth building?
- What will it cost per month to run, not only to build?
A vendor who answers the third question with ‘we test it manually’ is telling you something important. My longer checklist is in how to choose an AI development partner.
To sum up: buy advice when you lack a decision, buy hands when you lack capacity, hire when the work is permanent, and pay the Big 4 premium only when the risk is organisational. If you are not sure which of these you need, that is exactly what our AI opportunity audit is for: two weeks, $5–10k fixed, a full money-back guarantee, and the fee is credited in full to any project signed within 60 days. Sometimes its conclusion is ‘hire an engineer’ or ‘buy a tool’, and that is a good result too. If you prefer to talk first, book a call with me.