Build or buy — whose numbers are you using
Every build-or-buy decision arrives with a cost model already attached. Whoever wrote it is paid, rewarded or judged by how the comparison comes out — the vendor, an integrator, your own engineering team. None of them has to be dishonest for the model to lean.
This applies even where the decision was never framed as build versus buy. An internal build that skipped the comparison still has a cost model. It is the team’s own, and nobody wrote a buy column to test it against.
01
Who wrote the maintenance line?
Somewhere on that slide is a number for what “build” would cost to maintain. Ask who wrote it, and what they gain from each answer. If it was filled in by the party selling “buy,” you are comparing an option with a seller’s estimate of its alternative.
Asking your own engineers fixes the source, not the stake: the team that would run a built system has a position in the answer too. Get the estimate in hours, not a competitive-analysis guess, and have it reviewed by someone who gains nothing from either result.
02
What does year three actually cost, not year one?
The first-year price is what the comparison is decided on. Year three is what you live with. Get licence escalation, integration hours and switching cost written down — not projected verbally in the room — before anyone signs anything. The comparison that matters is the one three years out, and it only appears on the slide if someone was asked to price it.
Could you rebuild this comparison on your own whiteboard — every line sourced, every author named, and what each of them gains from each answer? If not, the decision isn’t yours yet. It belongs to whoever wrote the lines you can’t account for.
“Because whoever builds the cost model has a stake in the answer — and so does everyone else positioned to check it.”