Looking to Hire Flutter App Developers but Not Sure What to Budget For

[RemoteState]

Okay so I have been getting quotes for the past two weeks and the range is honestly making my head spin.
We are trying to hire flutter app developers for a fintech-adjacent app, nothing crazy in terms of features but it needs solid security and clean performance since it deals with user financial data. One agency quoted us $25k. Another quoted $90k for what sounded like basically the same scope. A freelancer offered to do it for $8k. At this point I genuinely cannot tell what a fair flutter app development cost even looks like anymore.

What is making this harder is that nobody explains why their number is what it is. They just hand you a quote and expect you to either accept it or walk away.

What I Have Learned So Far While Trying to Make Sense of This

Talked to a few people who went through this recently and started digging into what actually drives flutter app development cost up or down. Here is what I am working with so far:
The biggest cost driver is not Flutter itself but backend complexity and third party integrations because Flutter is the easy part compared to building secure APIs and payment systems behind it

When you hire flutter app developers through an agency you are usually paying for project management and QA on top of dev hours which explains some of the price gap with freelancers

A flutter mobile app development service that quotes way below market either has a less experienced team or is planning to cut corners somewhere you will not notice until later

Ask for a breakdown by feature not just a flat number because that is the only way to actually compare quotes apples to apples

Security heavy apps like fintech or healthcare always push flutter app development cost higher because of additional testing, compliance work, and encryption requirements that simpler apps do not need

Cheaper does not always mean worse and expensive does not always mean better, what matters more is whether they can explain exactly what you are paying for

Still Figuring This Out
Leaning toward the agency in the middle price range right now mainly because they were the only ones who actually broke down their quote line by line instead of just throwing a number at us. If anyone has gone through this recently and can share what you ended up paying and whether it was worth it that would genuinely help. Trying to avoid either overpaying or getting burned by a bargain deal.