The dominant factor is rarely the technology stack — it is almost always how much is still undecided. Every ambiguity in the requirements becomes a contingency somewhere in the quote. A team that does not know what happens on the unhappy path has to assume the worst. Spending a week on requirements work often reduces the total much more than negotiating the rate.

Integrations remain the next major multiplier. A feature that touches only your own data is easy to estimate; the same screen connected to a legacy ERP is another matter entirely. The unknown lives in the third party: undocumented APIs, long certification processes, fields that mean something different on each side. Ask each bidder to list every external system, as this is the usual source of overruns.

Non-functional requirements can easily double the estimate. An application used by a handful of staff has almost nothing in common with the same idea handling public traffic. Security reviews, uptime targets, performance under load, audit logging and localisation each add measurable effort. Put them in the brief or expect them priced as extras.

The team you are quoted changes the arithmetic. A day rate tells you very little on its own: one senior developer at a premium rate can be cheaper per delivered feature than two juniors who require supervision and rework. Check too who else is billed: coordination, testing, edtech web development services release engineering and analysis are real work, but they should be itemised.

The quoted figure is not the total cost. Plan for infrastructure, subscriptions and graphql vs rest licences, blockchain web development company monitoring and a change budget annually. A common working assumption says that software in active use consumes a recurring percentage of its original build cost annually for updates, security patches and small improvements. Leaving it out of the budget remains the classic mistake.