Not really. IIRC, they pay all of the "Payment Processor" money beyond their costs back to the carriers (though I'm not sure what happens with WiFi-only devices

Not really. IIRC, they pay all of the "Payment Processor" money beyond their costs back to the carriers (though I'm not sure what happens with WiFi-only devices). I suspect, but can't prove that they're acting out of ecosystem concerns like uniformity and conversion rates. Even now, the enforcement is pretty lax. I've been looking at some random apps and it surprised me how many asked for off-market donations and the like. Perhaps donations that don't unlock features fall under the same exception that permits third-party payment for physical goods and digital goods [i.e. music or ebooks] (what I've thought of as the Amazon exception).