* They have for years turned a blind eye to apps that sell things that aren't "digital goods" - so the Barnes & Noble app can sell you a physical book and pay $0 to Apple, but if they sell you an ebook in any way in the app, they owe 30%. But if they sell you an ebook in Safari, back to $0.

All of it's purely arbitrary and based on whatever the max Apple thinks they can skim from every transaction based on what leverage they have. The App Store has corrupted Apple into a form I don't even recognize anymore.