Receiving and refunding money to an App Store user

Question

Payment systems

There is an application where goals are set that the user wants to fulfill by depositing a certain amount from $1 to $100. This amount is withdrawn from his account and if he has reached the goal, then it is returned, if not, then it is not returned.
Arbitration decides whether to return the money - a person who is entrusted by the owner of the money or he controls himself. How can this be done without paying % to AppStor?

Answer 1

Legally nothing.