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Build vs buy: a decision framework you can defend
Build versus buy is a financial decision dressed as a technical one. Four inputs decide it: process fit, growth in licence cost, the cost of workarounds, and how likely you are to want to leave.
Outcomes
- Score process fit honestly, feature by feature
- Model licence cost at your three-year headcount, not today's
- Price the workarounds you already perform
- Ask what leaving would cost under each option
- Consider building only the differentiating layer
Problems this solves
The decision is made on price alone
Total cost over three years, fit to process and exit cost matter more than the initial quote.
Nobody owns the decision criteria
Write the criteria and weights before seeing demos, otherwise the last presentation wins.
Reversibility is never discussed
Prefer the option that is cheapest to undo when the answer is genuinely close.
How delivery runs
- 01
Write the process down
One page per workflow, including the exceptions that actually consume time.
- 02
Score against criteria
Fit, integration, cost over three years, exit cost, and who supports it.
- 03
Prototype the risky part
Where the decision hinges on one unknown, spend a week proving it rather than arguing.
- 04
Decide and phase
Commit, then start with the smallest phase that produces value.
Build or buy
Buy something existing when
- Commodity processes: accounting, payroll, email, helpdesk
Build custom when
- Your differentiating workflow and the integration layer between systems
The question is rarely all-or-nothing; it is which layer to build.
What moves the price
Integration effort
Present in both options, and consistently underestimated in the buy case.
Internal capacity
Building requires product ownership time from your side, every sprint.
Change frequency
Processes that change often are expensive to keep configured in a rigid product.
Where projects go wrong
Sunk-cost continuation
Set a review point where stopping is an acceptable outcome.
Vendor lock-in
Check data export, API access and contract terms before signing.
FAQ
Questions buyers ask
What if we are not sure?+
Run a short discovery. Two to three weeks of evidence is cheaper than either wrong decision.
Can we start with buy and build later?+
Often the best route — integrate now, replace the part that constrains you when it actually constrains you.
Related pages
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