1. App quality screening
2. App promotion/distribution
3. In app purchasing
Ask any reasonable dev if they are willing to foot a fixed cost to get their app screened, a fixed cost per app download (bandwidth), and variable cost to get their app promoted in the store (not everyone needs this) and they would agree. What pisses people off is Apple’s entitlement to the revenue of a company when there is no value add from Apple after the customer has gotten the app. So Apple is using their monopoly to force #3 on developers at no less than 30% of revenue.