The 30% is not just for music though. It's for any non consumable product sold within the apps including points, coins, level unlock and all the other IAP transactions.
I know what it encompasses. I'm not soley against having a fee for one time purchases. Apple is the payment processor and should receive something for the infrastructure and services of that and the App store. The question is, is 30% too much for the market (of developers not consumers) to bear? this isn't 2008 anymore with small(ish) volume and the need for larger margins to help get the infrastructure up and running. it's 2016 with a sheer mass of volume of billions of users. is 30% still reasonable? Keep in mind that the going rate alone for payment processing from most credit cards for merchants is roughly < 5%. Apple is asking 30% in the first year, and 15% ongoing after for doing nothing but payment processing (after the initial download).
We've already stated that Spotify needs to re-examine their business model. But that doesn't mean Apple isn't in a position either that they need to look at their own models as well.