What is your argument here? That Apple's services cost literally
nothing to provide?
Apple provides developers access to an enormous marketplace that they run. A marketplace with hundreds of millions of "high value" customers pre-configured for payments. All sorts of related services are included, such as fraud detection, currency conversion, etc...
What do you think Apple does? Just skim 30% off the top without doing anything else?
Seriously, some people live in this fantasy world where all products should be worth 100% of their raw material cost, and services should cost only what the showroom rent+aircon costs to provide.