Guides5 min read
Why we stopped billing by the hour
The hour stopped measuring anything once AI began writing the code. We price the result, with one plain rule on each offer that keeps its price fixed.
Mercury Labs
The hour stopped measuring anything once AI began writing the code. We price the result, with one plain rule on each offer that keeps its price fixed.
We stopped billing by the hour because the hour stopped measuring anything. When AI writes much of the code, how long a piece of work takes has little to do with what it is worth, and a supplier paid by the hour earns most when it is slowest. So we now price the result.
Time and materials means you pay for the days worked, whatever they produce. Fixed-price work means you pay for a result, however long it takes the supplier to deliver it.
For most of the history of software, the expensive part was writing it. An estimate in days was a fair guess at the cost, because days of a skilled person's time were the cost.
That is no longer true of our own work. Our engineers now direct AI coding agents: they describe the change, the agent writes it, and the engineer reviews and tests what comes back. The writing takes minutes. What takes time, and skill, is deciding what should be built, breaking it into pieces an agent can do well, and catching the places where it was wrong.
The speed is not automatic, and the evidence says so. A controlled study in 2023 found developers finished a set task 55% faster with an AI assistant. A study in 2025 of experienced developers working on their own large projects found them 19% slower. The tools are the same. The difference is in how the work is organised around them, which is the part a client is really paying for.
Three things.
We charge for a result, and we attach one plain rule to each price so that it can stay fixed. Without the rule, a fixed price is either unbelievable or a loss.
| What we sell | Price | The rule that keeps it fixed |
|---|---|---|
| The Company Twin | From £75 a user a month | A product: you pay for the people who use it |
| Unlimited development | £15,000 a month | One product, and we work with you in writing, not in meetings |
| AI security audit | £1,000, once | One application: its code, its dependencies and what it exposes to the internet |
| AI transformation | Scoped with you | A programme with an agreed shape, priced before it starts |
| Dedicated engineering | Per engagement | One stage at a time, each priced before it begins and ending in a go or no-go |
Something real, and it is better said plainly. You are no longer buying a named person's Tuesday. On a subscription you cannot split the team across three products, and you will not get a standing weekly call. Requests, questions and updates happen in writing, in your Slack or Teams, and the thread is the record.
In return the risk moves to us. If a request takes three times as long as we expected, that is our problem and not a change request. You know what the month costs before it starts.
When nobody can say what the result is. Open-ended research, where the honest answer to "what will we have at the end?" is "we do not know yet", is hard to price any other way. It also makes sense when you want extra people to direct yourself, inside your own team and your own way of working. That is hiring by another name, and the day rate is a fair way to pay for it.
04 stages
What do I pay if the work takes you half the time you expected?
Watchpoint
If the answer is half, the supplier has no reason to get faster.
What happens when my priorities change mid-month?
Watchpoint
A change request and a new quote for every change is the hourly model in disguise.
Who carries the cost if it overruns?
Watchpoint
If it is you, the price was never fixed.
How will I see progress without a meeting?
Watchpoint
If progress only exists in a status call, you are paying for the call.
Unlimited development is the plainest example of the fixed price in practice: a senior engineering team for one product, with as many requests as you need and no hours to count.