Uhhhh, not a percentage ? Do you imagine AWS billing you a % of your revenue instead of a given price for a given service ?
Give a price to be listed in store, to be reviewed, to be downloaded by a user, ... And let company pay what they owe you. Let them pay through the provider they can negotiate and then pay you back the cost they owe you.
It's ridiculous that it doesn't matter if my app has a 5$ sub or a 50$ sub, I owe them 30% anyway. What they provided is the same in both cases, they should be able to price it out to me. Their current pricing structure is not setup like a fee for services and infrastructure usage, it's setup like a tax.