The biggest cost driver is rarely technology — it is almost always how much is still undecided. Every open question in the requirements turns into a buffer inside the number you receive. A team that does not know the edge cases must assume the worst. Spending a week on requirements work can cut the overall figure by far more than negotiating the rate.
Connections to other systems tend to be the next major multiplier. A form that saves data is low risk; the same functionality connected to a legacy ERP is not. The effort lives in the third party: rate limits and sandbox access, slow approval cycles, inconsistent data. Ask the estimator to break integrations out as separate items, azure development services as this is the usual source of overruns.
Quality attributes can easily double the budget. A tool used by a small internal team is a very different build from the same idea handling thousands of external customers. Audit and compliance requirements, high availability, scalability, traceability and multi-language support all add weeks of work. State them early or you can expect the estimate to move later.
The mix of people behind the number changes the arithmetic. An hourly rate says very little on its own: an experienced engineer at a premium rate can be cheaper overall than two inexperienced developers who need constant review. Ask as well which roles are billed: coordination, quality assurance, release engineering and analysis have to be done by someone, but they must be visible in the estimate.
The build price is rarely what you will actually spend. Expect infrastructure, paid APIs, observability and a change budget annually. A useful planning figure is that seo agency for software factories in active use needs a recurring percentage of the original budget every year simply to stay current. Treating the launch as the finish line is the classic mistake.
