It seems to me that it will be difficult to answer this question unambiguously, since each project is individual and the amount of work on it may have a different cost. Regardless of the price, you need to understand that the convenience and attraction of the guest is the main thing in your application. Therefore, it is worth entrusting its design to experienced specialists, as an option, you can order a design from this one: https://www.halo-lab.com/services/mobile-application-design-services app design company.