I'm going to post here a similar argument to what I posted at the other place:
I think there are several separate concerns:
Concern 1. Should Apple have some form of license fee for iOS SDKs and technologies?
Concern 2. Does Apple deserve a share of all revenue that occurs on iOS?
Concern 3. How should Apple be generate the revenue to cover the costs of running the App Store?
Concern 1
If the answer to 1 is yes then all apps that generate revenue on iOS should pay it, right now there are far too many categories of application that pay nothing, in fact some of the most profitable Apps on the platform pay nothing, putting the lie to the idea that the exceptions are based on some sort of generosity on Apple's part.
Concern 2
If the answer two 2 is yes then there should be no reader app exception and even transactions on the web should be paying a percentage to Apple, after all Apple built the platform on which the mobile transaction is taking place.
Concern 1 and 2
The argument is that the 30-15% fee is what covers these two points, I however think that the inconsistent application and number of exemptions show this line of argumentation to be pure marketing spin.
I think the reason Apple has so many exceptions is because they know how important Apps are to the success of the iPhone and that if they actually had fair policies they risk alienating some of the biggest and most important developers. Hence, they put in place policies that appeal and keep the big names on the platform at the expense of a coherent App Store policy. As others say, these are perfectly rational business decisions, but if, as the EU says, platforms have to operate fairly, these policy choices put apple at risk of fines and further regulatory scrutiny.
I actually think the answer to 1 is yes and to 2 is no.
I think Apple has pushed iOS so much further than macOS because of App Store revenue and I think that some form of CTF applied fairly (with small business exceptions) would make the system much fairer to everyone. If a share of sales is the form that takes then it needs no exceptions, digital goods, physical goods, subscriptions, reader apps, they should all pay that share of revenue. If apps would be driven from the platform with this approach that is likely a sign that the percentage is too high rather than that the fee itself is wrong.
I personally think splitting the commission and CTF into two separate components (like they do for DMA compliance) is a good path forward. The 50 cents per download might be too high and there should probably be exemptions for apps that earn no revenue but generally I think the CTF plus commission if using Apple's payment system is a good compromise.
Concern 3
The answer to 3 could be some sort of hosting and review fee (maybe with carve outs for free apps or first X downloads are free). Again, this should be applied uniformly and fairly to all apps.
Edit:
I want to also add that I think that a fairer and better route to go would be to move away from the high commissions on transactions and have something like the CTF plus low per transaction commissions worldwide (though, as I said above, if it was universal I think that $0.50 per download would likely be too high). I think the way the have given developers the option of continuing the current terms (no CTF but no alternative payment options) is a way of steering devs to use the old terms and is likely going to be a regulatory problem for Apple in the future.