The biggest cost driver is not the choice of framework — it is unclear scope. Each unanswered question in the requirements turns into a contingency in the estimate. A vendor that does not know what happens on the unhappy path has to assume a pessimistic case. Spending a week on a proper discovery can cut the final cost far more than any rate negotiation.
Integrations are the second big multiplier. A screen that writes to your own database is easy to estimate; the same screen connected to a payment provider and a CRM is another matter entirely. The cost hides in the third party: poor documentation, slow approval cycles, inconsistent data. Ask any vendor to list every external system, since this is where estimates break.
The requirements nobody writes down can easily double the budget. An application used by twenty people is a very different build from the same feature set serving public traffic. Compliance work, high availability, bespoke software development cost load handling, audit logging and livewire vs alpine js multi-language support each add real engineering time. Write them down at the start or you can expect the estimate to move later.
The team you are quoted matters a great deal. An hourly rate tells you very little on its own: one senior hire dedicated aiohttp developer at a higher rate can be cheaper per delivered feature than a pair of junior developers who require constant review. Check too what else appears on the invoice: delivery management, elearning software development quality assurance, release engineering and design have to be done by someone, but they should be named rather than hidden inside a blended rate.
The build price is rarely what you will actually spend. Plan for infrastructure, third-party licences, monitoring and a maintenance allowance annually. A useful planning figure holds that any production system consumes a meaningful share of the original budget per year for updates, security patches and small improvements. Treating the launch as the finish line has always been the classic mistake.