The dominant factor is not the choice of framework — it remains unclear scope. Every ambiguity in the brief becomes a contingency in the estimate. A supplier that cannot see the edge cases must assume a pessimistic case. Putting two weeks into a proper discovery often reduces the total far more than haggling over hourly rates.
Connections to other systems are another reliable source of cost. A feature that touches only your own data is predictable; the same functionality connected to a legacy ERP is a different problem. The effort sits in the counterparty: poor documentation, long certification processes, data that does not match your model. Ask any vendor to price integrations separately, since that is where the numbers slip.
Non-functional requirements quietly rewrite the estimate. An internal tool used by a handful of staff is a very different build from the same idea serving a hundred thousand ongoing software support company users. Security reviews, availability guarantees, scalability, traceability and localisation each add real engineering time. Write them down at the start or you can expect them priced as extras.
The mix of people behind the number changes the arithmetic. An hourly rate says almost nothing on its own: a senior engineer at twice the price is often cheaper overall than two inexperienced developers who require heavy code review. Also ask which is better laravel or django roles are billed: project management, quality assurance, laravel vs .net release engineering and analysis have to be done by someone, but these should be itemised.
The build price is never the total cost. Expect cloud costs, third-party licences, hire python developers monitoring and a maintenance allowance annually. A reasonable rule of thumb holds that any production system needs a meaningful share of its original build cost per year in fixes, updates and small changes. Treating the launch as the finish line remains the most common budgeting mistake.