The biggest cost driver is not the choice of framework — it remains uncertainty. Every open question in the specification is converted into a buffer inside the number you receive. A team that cannot see what happens on the unhappy path must assume the more expensive option. Spending a week on a proper discovery can cut the total far more than haggling over hourly rates.
Connections to other systems tend to be another reliable source of cost. A form that saves data is easy to estimate; the same feature connected to a legacy ERP is a different problem. The cost hides in the other system: poor graphql vs rest documentation, long certification processes, fields that mean something different on each side. Ask each bidder to break integrations out as separate items, since that is where the numbers slip.
Non-functional requirements silently change the number. An internal tool used by a small internal team costs far less than the same idea handling thousands of external customers. Audit and compliance requirements, high availability, scalability, audit logging and localisation each add weeks of work. State them early or you can expect the estimate to move later.
Who actually does the work matters. A rate card says very little on its own: python development experts one senior developer at a higher rate is often cheaper overall than a pair of junior developers who require constant review. Ask as well what else appears on the invoice: project management, quality assurance, release engineering and UX design have to be done by someone, but they should be named rather than hidden inside a blended rate.
The quoted figure is never what you will actually spend. Expect cloud costs, paid APIs, observability and an ongoing support budget for every year the software development for regulated industries runs. A useful planning figure says that any production system requires a noticeable fraction of the original budget per year in fixes, updates and small changes. Leaving it out of the budget has always been the most common budgeting mistake.
