What changes the effort
A simple form may need private documents, approvals and a connection to a system without an API. Several views can also share the same data. Ask for a workflow-based estimate, including exceptions and corrections.
Data preparation belongs in the quote
Identify duplicates, missing keys and documents that are not linked to records. An authorized sample helps define migration effort and unresolved assumptions before fixing the price.
Compare delivery, not just the total
Check code and account ownership, access, testing, training and post-launch defect handling. A smaller proposal may be sufficient, or may omit a necessary part of the process.
Start with a complete first version
For a purchase request: entry, attachment, approval or return, history and lookup. Extra integrations can follow. Name the person who accepts the work and the conditions for each milestone.