The cost of creating an application varies in the tens of thousands of dollars, so if you don't have much experience in this, it is better to entrust the people who know better than you. I know one good company  https://surf.dev/flutter-app-development-cost/  , there are guys who are doing Flutter app development for about 10 years and know exactly how to calculate the right flutter app development cost. So I advise you not to doubt, go to their website and cooperate with professionals!