The dominant factor is never technology — it is almost always unclear scope. Every open question in the requirements turns into a buffer inside the number you receive. A vendor that cannot see the exceptions and edge cases will assume the more expensive option. Putting two weeks into requirements work often reduces the final cost by far more than negotiating the rate.
Integrations tend to be another reliable source of cost. A screen that writes to your own database is predictable; the same functionality wired into a legacy ERP is a different problem. The unknown lives in the other system: poor documentation, waiting on someone else’s team, data that does not match your model. Ask any vendor to break integrations out as separate items, since this is where estimates break.
Non-functional requirements quietly rewrite the budget. An application used by a handful of staff is a very different build from the same idea handling public traffic. Compliance work, high availability, scalability, data retention rules and multi-language support each add weeks of work. Put them in the brief or expect the estimate to move later.
The team you are quoted matters. An hourly rate says very little on its own: a senior engineer at a premium rate can be cheaper overall than two inexperienced developers who require heavy code audit services review. Ask as well what else appears on the invoice: project management, quality assurance, docker web development company DevOps and UX design are real work, but they must be visible in the estimate.
The number in the proposal is rarely the full cost of ownership. Expect hosting, paid APIs, logging and alerting and mvp development company a maintenance allowance for every year the affiliate software development company runs. A useful planning figure holds that a live system needs a recurring percentage of its original build cost per year simply to stay current. Treating the launch as the finish line has always been the classic mistake.