Build vs. buy: what does document infrastructure really cost?

Effort (in person-months) becomes a cost using a fully loaded developer day rate for the region your engineers are in — these range roughly from €420/day to €850/day depending on region, and you can override the default. Timeline is effort divided by your team size (three engineers by default), with a 20% buffer for integration and stabilization, and a four-month floor.

Ongoing cost has three parts: maintenance, estimated at roughly 20% of build cost per year — the typical ownership tail for custom software; infrastructure, which scales with document volume; and compliance overhead, which is higher for advanced signatures and higher again for qualified signatures, which require an ongoing relationship with a Qualified Trust Service Provider rather than a one-time integration.

Whatever your current path costs — manual work, a partner-built workaround, license spend across multiple tools, or developer time on custom code — keeps costing that while the in-house build is underway. That ongoing cost, for the length of the build timeline, is the fourth component of your three-year total.