I'm not sure how you got from the title to the question. How are these related? I can tell you from my current experience with pricing, businesses seem to hate

I'm not sure how you got from the title to the question. How are these related? I can tell you from my current experience with pricing, businesses seem to hate variable pricing, even when the fixed price (monthly fee) is greater than they would pay if paying a percentage (though my pricing was usage based not as a percent of x). Percent feels like a tax, and nobody likes taxes. You're probably thinking of it from the perspective of "the more money you make, the more money I make, I'm only charging you for the service". But that is likely not how the business is thinking of it. They're thinking that they do all the work, and you can't even give them a price of what they are going to pay. You'll just "take" more for everything that they work so hard to build. If what you are providing is something they can't live without, like the App Store, then you can probably get away with charging a percent, and your customers may hate you for it.