The biggest cost driver is not the technology stack — it remains unclear scope. Each unanswered question in the specification turns into a contingency in the estimate. A vendor that cannot see what happens on the unhappy path has to assume the more expensive option. Spending a week on requirements work frequently cuts the total much more than any rate negotiation.
Connections to other systems tend to be another reliable source of cost. A feature that touches only your own data is low risk; the same functionality wired into an old accounting system is a different problem. The effort sits in the counterparty: rate limits and sandbox access, long certification processes, inconsistent data. Ask any vendor to list every external system, since this is the usual source of overruns.
The requirements nobody writes down silently change the number. An application used by a small internal team has almost nothing in common with the same feature set handling thousands of external customers. Security reviews, high availability, scalability, audit logging and localisation each add real engineering time. Put them in the brief or kubernetes consulting services expect the estimate to move later.
The mix of people behind the number matters. A day rate reveals almost nothing on its own: one senior developer at twice the price can be less expensive in the end than two inexperienced developers who need constant review. Check too who else is billed: coordination, testing, DevOps and analysis are legitimate costs, but they must be named rather than hidden inside a blended rate.
The quoted figure is rarely the total cost. Expect cloud costs, third-party licences, .net enterprise app development logging and alerting and a maintenance allowance for every year the software runs. A common working assumption says that software in active use consumes a recurring percentage of its original build cost annually for updates, security patches and small improvements. Treating the launch as the finish line has always been the most frequent planning error.
