Landlords have exclusive use of land, a limited resource. If I am running a clothing brand and I want to have a store in a particular city, my options are to build a store on empty land very far from the city center, or to negotiate with the person who has the land.n If I want to have a store in a mall, I certainly can't just built on my own, and in many cities, there's probably not even another mall to provide competition.

Apple is charging for use of the Apple App Store platform. They are not charging for the Android Play Store platform. They are not charging for anything happening anywhere else. There is no exclusive resource like land involved, as demonstrated by the fact that Android was able to build the Play Store.

I don't think it makes any sense to say that Apple has a monopoly over use of their own product, since a monopoly is about control of a market. But if we're going to make that claim, we should definitely say that each mall owner has a monopoly over use of that mall! That is at least as sensible as saying that Apple and Android both have monopolies over their respective competing products.

And I think that the concern people have isn't whether the price has been decided by the market - it clearly has, and tons of participants are willing to participate even with the 30% cut - the question is whether the price is fair in a moral sense. I do agree with the answer that it is not. But I think you have to ask the right question to get the right answer.