What rebuilding a buying group's system really costs

No software firm publishes prices for this kind of project, and the excuse is always the same: it depends. That is true. It is not a reason to leave a general manager standing in front of a board with no order of magnitude at all. So here are ranges, what moves them, and the three cost items nobody prices at the start.

Why nobody gives you a figure

There are two reasons, and only one of them is honest. The honest one: the scope really does vary by a factor of five between a group that wants a member portal and one that wants its entire rebate engine rebuilt, and a figure quoted before seeing your scales is a figure invented. The less honest one: a published price becomes a ceiling in the negotiation, and most firms would rather discover your budget than reveal theirs.

The consequence is predictable. You consult three suppliers, you receive three quotes that range from one to three, and you have no way of telling which of them understood the problem. The cheapest one has usually understood the least — not because it is dishonest, but because it has not yet met the rules nobody wrote down.

The only firm price we publish

Scoping plus prototype, three weeks, €6,000 to €10,000 excluding VAT depending on the scope, deducted in full from the project fee if the project goes ahead. That is not a commercial trick, it is the only honest way to price the rest: two workshops with the people who actually run the process, a working prototype on the most painful part of it, and a firm quote for the complete project.

Everything below that line is an order of magnitude. Useful for building a budget envelope and for reading someone else's quote — not a quote itself.

Orders of magnitude, batch by batch

A management platform for a buying group is not one price, it is six or seven. Thinking in batches is what lets you stage the spend across financial years, and it is also the fastest way to spot a supplier who has not understood the work: a firm that cannot break its own quote down into batches has not thought about the sequencing either.

A group almost never buys every batch at once. A realistic first year covers two or three of them: €50,000 to €110,000. The complete platform, spread over two or three financial years, most often lands between €110,000 and €250,000. Below €50,000 you are buying one process, not a system. Above €250,000, ask what exactly is being built that a group of eighty companies needs.

What actually makes a budget explode

Four things, in the order in which they hurt. None of them is technical.

• Unwritten rules. Every group applies exceptions that live in one person's head — a supplier whose tier was adjusted by hand in 2019, a member with a bespoke split. Each one is small; twenty of them rewrite the specification mid-build.
• Data migration. Fifteen years of duplicate suppliers, companies renamed twice and scanned agreements with no metadata. The cost is driven by how clean the data is, not how much of it there is — a point almost every initial estimate gets backwards.
• The number of people entitled to decide. One project sponsor with real authority costs a fraction of a steering committee of nine where every arbitration waits for the next meeting. This is the single most reliable predictor of overrun we know.
• Interfaces with the existing landscape. Accounting exports, single sign-on, an ERP that only reads flat files. Each interface is a small piece of work and a large negotiation with a third party who has no deadline.

Three of those four can be handled before development starts, which is precisely the point of a scoping phase. The fourth — the decision circuit — is yours to fix, and no supplier can fix it for you.

The three items no quote contains

The recurring cost, and the cost of doing nothing

Budget between 12 and 20 % of the initial development cost per year for maintenance and small evolutions, plus hosting — a few tens to a few hundred euros a month at these volumes, and closer to the low end than most people expect for a platform serving eighty companies. Together, expect a recurring cost of 15 to 25 % of the initial budget each year.

That ratio matters more than the build price. A management system of this kind lives eight to twelve years. Over that lifetime the recurring cost exceeds the initial one, which means the question to ask a supplier is not only what the build costs, but what year three costs — and who owns the code if you decide, in year four, that you would rather someone else maintained it.

Against that recurring figure sits the one the board never sees, and it is the only one that makes the comparison meaningful. Rather than assert a figure, compute your own. Take the days your permanent team spends on one declaration campaign — collecting, chasing, retyping, reconciling — and multiply by their fully loaded daily cost. Add the days lost each time a supplier disputes an amount and the breakdown has to be reconstructed by hand. Add the cost of the annual statement being late.

Then add the two items that never appear on a spreadsheet: the operational risk of a calculation only two people can run, and the decisions your board stops taking because nobody can simulate them. Groups that go through this arithmetic honestly usually find that the recurring cost of the current situation is of the same order as the annual amortisation of the platform that would replace it. That does not make the project free. It makes it a comparison rather than an expense.

How to read a development quote

• A price per batch, with what is included and what is explicitly excluded from each. A single global figure hides the arbitrations you will be asked to make later.
• Acceptance written into the quote: who tests, on which data, against which list, and what happens when a test fails.
• Migration priced as a line item, not folded into a footnote. If it is not priced, it has not been looked at.
• The rule for scope changes: how a new requirement is estimated, and who signs before work starts.
• Maintenance priced in the same document as the build, with a committed response time.
• A reversibility clause: source code, documentation and data handed over, with no repurchase condition.

A development quote that fits on one line is not a price, it is a bet, and you are the one carrying it. The right instinct is not to look for the cheapest quote but for the one broken down most finely — because a supplier who can break the work down is a supplier who has understood the process, and the level of detail in a quote is the cheapest quality signal you will ever get.