There is no honest single price for an app. A first release that lets one type of user finish one job is a different product from an app with accounts, payments, offline use, and an admin team.
Ask what the first version must do, who is excluded on purpose, and which systems it has to talk to. Those answers move the cost more than the choice of iOS or Android. Store release, the month of fixes after launch, and a way for the team to change copy also belong in the same estimate.
Sovassa does not publish a calculator. A consultation can give a range after the job is clear. A number before that is a guess.