No, there won't be any additional cost from us. Once we build your app, we'll provide you with the app files. You can then submit these files to Google Play and the Apple App Store using your own developer account.
For Android, you'll receive the APK and AAB files, while for iOS, you'll receive the IPA file. You won't need to pay us extra for the app submission to the App/Play stores. However, you'll need to create your own developer accounts for Google Play and the Apple App Store. They have their fees.
If you prefer, you can also hire our expert service to handle the app submission on your behalf. Find more details about this option in our informative article: