This is true, generally speaking if the fee is invisible then people don't care. I could see developers simply adding a 2nd line item "Apple Fee 30%" and gross

This is true, generally speaking if the fee is invisible then people don't care. I could see developers simply adding a 2nd line item "Apple Fee 30%" and gross up the price by that amount. Then let Apple answer the questions why there is a 30% fee added in their products, but not others (if that's the case).