What Actually Drives Software Development Costs
The single largest cost driver is never the choice of framework — it is almost always uncertainty. Each unanswered question in the brief turns into a contingency in the estimate. A vendor that does not know what happens on the unhappy path has to assume the worst. Putting two weeks into requirements work can cut the overall figure by far more than negotiating the rate.
Connections to other systems are another reliable source of cost. A screen that writes to your own database is low risk; the same functionality talking to a legacy ERP is not. The unknown lives in the counterparty: rate limits and sandbox access, symfony vs laravel performance waiting on someone else's team, fields that mean something different on each side. Ask each bidder to price integrations separately, since this is the usual source of overruns.
Non-functional requirements can easily double the estimate. An internal tool used by a handful of staff has almost nothing in common with the same functionality serving a hundred thousand users. Compliance work, high availability, load handling, data retention rules and flutter vs react native multi-language support add measurable effort. State them early or else expect the estimate to move later.
The team you are quoted matters a great deal. A rate card says almost nothing on its own: one senior custom government agency software development developer at a higher rate is often cheaper overall than a pair of junior developers who need constant review. Ask as well which roles are billed: delivery management, quality assurance, infrastructure work and golang development company UX design are real work, but they should be itemised.
The number in the proposal is rarely the total cost. Expect infrastructure, subscriptions and licences, monitoring and a maintenance allowance annually. A useful planning figure says that any production system requires a recurring percentage of the original budget every year in fixes, updates and small changes. Leaving it out of the budget is the classic mistake.