Apps you have developed are published through your developer accounts.
Opening a Google Play Store Developer Account costs $25, including VAT (Value Added Tax). This fee is paid only on account opening and directly to Google; It has nothing to do with MobiRoller.
You can read our relevant article How to Open a Google Play Console Developer Account?
Opening an Apple App Store Developer Account costs $ 99 including VAT. This fee repeats annually and is paid directly to Apple; It has nothing to do with MobiRoller.
You can read our relevant article How to Create an Apple Developer Account?