The biggest cost driver is not the choice of framework — it is how much is still undecided. Every open question in the requirements is converted into padding somewhere in the quote. A supplier that has no visibility into the edge cases will assume a pessimistic case. Putting two weeks into a proper discovery can cut the final cost much more than haggling over hourly rates.
Connections to other systems tend to be another reliable source of cost. A feature that touches only your own data is easy to estimate; the same feature connected to a legacy ERP is another matter entirely. The unknown lives in the third party: poor documentation, waiting on someone else’s team, inconsistent data. Ask any vendor to price integrations separately, since that is where the numbers slip.
The requirements nobody writes down silently change the budget. An application used by a handful of staff costs far less than the same idea handling a hundred thousand users. Compliance work, uptime targets, load handling, data retention rules and accessibility add measurable effort. State them early freelancers or dedicated team else expect them priced as extras.
Who actually does the work matters a great deal. A day rate reveals almost nothing on its own: an experienced engineer at a premium rate is often cheaper overall than two inexperienced hire react developers who require heavy code review. Also ask who else is billed: project management, QA, infrastructure work custom fintech and crypto software development analysis are real work, but these should be visible in the estimate.
The quoted figure is never the full cost of ownership. Expect cloud costs, third-party licences, monitoring and a change budget each year. A useful planning figure says that any production system consumes a meaningful share of the initial investment annually in fixes, updates and small changes. Treating the launch as the finish line has always been the classic mistake.