Roughly 2.5x separates the cheapest and the dearest quote you will receive for the same senior AI engineer in Europe. The gap is not skill. It is how many people sit between that engineer and your problem, and who absorbs the cost when the scope moves in month three.
“AI software development company” describes at least five business models with different cost structures and different failure modes. Buyers who put all five on the same shortlist end up comparing a day rate against a fixed price against a placement fee, which tells them nothing.
The five categories
| Category | What you are buying | Senior day rate, Europe | How it usually fails |
|---|---|---|---|
| Global systems integrators | A contract, a delivery method, a staffing pyramid | €900–1,500 | Three seniors in the pitch, one on the project |
| Big-4 consulting practices | Board-level cover and audit-grade documentation | €1,200–2,000 | Strategy is strong; the build is subcontracted |
| Boutique AI agencies | Genuine depth in one narrow area | €700–1,100 | Founder-led capacity; one departure empties the team |
| Talent marketplaces | A filtered CV and a payments rail | €350–700 | No bench, no replacement, nobody reviews the code |
| Nearshore staff augmentation | Named engineers on time and materials | €450–700 | You must supply the technical direction |
Those bands are directional and move with region, stack and contract length. Our current day rate bands by role and seniority are published and updated rather than quoted per enquiry.
The price is built differently, not just set differently
A fixed-price proposal for AI work carries a risk premium, typically 25% to 40% over the same scope on time and materials. That premium buys certainty about the invoice, not about the outcome, and the vendor prices it against the worst plausible version of your requirements. With retrieval systems and agents, the worst plausible version is far from the expected one, because nobody knows the retrieval quality of your documents until someone loads them.
The larger the firm, the more of the rate goes to people who are not writing code: engagement management, quality assurance, account coverage, bench cost. That overhead is real work in a 40-person programme with three workstreams. On a five-person build it is 20% to 30% of the invoice buying you status reports. We set out when each shape is worth paying for in time and materials versus fixed price.
Four checks that predict the outcome
- Ask for the names and CVs of the engineers who start in week one, and a contractual clause requiring your approval on any substitution. Vendors who staff from a pyramid will resist this, which is the answer.
- Ask what share of billed hours on their last delivered project came from engineers with more than five years of experience. A number below 50% means you are funding training.
- Ask who owns the prompts, evaluation sets, fine-tuning data and pipeline code. Standard terms at several provider types leave the vendor with a perpetual licence to reuse everything.
- Ask what happens in month four when the scope changes. A change request priced at 15 days and signed by two directors is a different operating model from a sprint reprioritisation.
A structured version of this conversation, with the questions that separate an engineering team from a sales team, sits in our guide to evaluating an AI engineering vendor in one call.
When renting engineers is the wrong answer
Our model is the last row of that table, and it fails in four situations.
If nobody on your side can set technical direction and accept or reject an architecture, rented engineers will build something competent that solves the wrong problem. Buy a managed outcome instead and pay for the estimation risk. If the work is under about 20 days, the onboarding cost dominates and a boutique fixed price is cheaper. If you need a signature that carries liability for a regulatory filing, no staffing arrangement provides it. And if you want a finished product rather than capacity, you want a product vendor.
Everywhere else, the question is narrower than the shortlist suggests: how senior are the people who will actually type, and what does a day of their time cost. Once you have those two numbers for each bidder, most of the difference between AI development providers resolves into arithmetic.