The biggest cost driver is not technology — it remains unclear scope. Every open question in the requirements is converted into a contingency somewhere in the quote. A supplier that does not know the exceptions and edge cases must assume the more expensive option. Spending a week on requirements work often reduces the total far more than any rate negotiation.
Connections to other systems tend to be the next major multiplier. A form that saves data is low risk; the same feature connected to an old accounting system is another matter entirely. The cost sits in the other system: poor documentation, long certification processes, fields that mean something different on each side. Ask any vendor to list every external system, as that is where the numbers slip.
Quality attributes silently change the budget. An internal tool used by a small internal team costs far less than the same functionality handling a hundred thousand users. Compliance work, symfony solution development uptime targets, load handling, traceability and multi-language support all add real engineering time. Write them down at the start or you can expect them to arrive later as change requests.
The team you are quoted changes the arithmetic. A rate card reveals almost nothing on its own: flutter development company an experienced engineer at a higher rate can be cheaper overall than two juniors who need heavy code review. Check too who else is billed: project management, quality assurance, release engineering and UX design are legitimate costs, but they should be itemised.
The number in the proposal is not the full cost of ownership. Budget for hosting, third-party licences, logging and alerting and a maintenance allowance annually. A useful planning figure holds that a live system needs a recurring percentage of the original budget every year in fixes, outsourced software development updates and small changes. Treating the launch as the finish line is the most frequent planning error.