Don't get me wrong, this statement isn't in support of Apple, I'm just saying that your analogy is bad.
What is not reasonable is for Apple to take a cut from transactions that do not need to involve them. If Epic sells hats in their own online store and don't use Apple as the payment processor, this costs Apple nothing. No bandwidth costs, no nothing.
If Apple wants to charge Fortnite whatever it costs to distribute Fortnite updates on the App Store + 30% on top as their fee for delivering that service, I am 100% sure Epic would be OK with that.
This is not what they are doing.
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Here's an extreme hypothetical to illustrate how Apple is using their monopoly position for rent-seeking:
Imagine you have an app that is downloaded 100 times in the App Store. It is not marketed, advertised, other otherwise promoted by Apple.
In total, it costs Apple pennies to provide this service to your customers. You never push an update to the App Store – it is always on version 1.0.0. You are already paying Apple $99 per year for the privilege of your app being in their App Store, so they're pocketing a tidy profit.
Now imagine that you offer a subscription service, which all 100 customers who downloaded your app are paying for. This subscription costs $100 a month.
Apple is not involved in the delivery of this subscription at all (except in the delivery of the original app, which you are already paying $99py for), but Apple wants to take $30,000 a month from you, for something that in total cost them pennies.
If that's not ludicrous rent-seeking, I don't know what is. Obviously this is an extreme, totally made-up example, but the entire point is that it is bad to insert yourself into a transaction where you are not providing any added value – charge at the point where you are involved. Do not use your monopoly position to force yourself into transactions where you really have no business being.
I don't see anybody complaining about Sony taking cuts and requiring transactions go through the PlayStation Network, even though purchasing things for Fortnite there does not in any way, shape or form need to involve the PlayStation Network to be properly facilitated.
Is there something I'm not seeing?
I do not think marketplace providers should be able to exert monopolistic pressure on developers that use their marketplace, full stop. I think it's anti-competetive and bad for the entire digital ecosystem as a whole.