It’s rent in the sense of rent seeking. You control an asset and let others pay for using it, if they want to. Rent seeking is not a very good thing but it’s a minuscule part of Apple’s business model. I also can’t see how a small developer can find it unfair, 30% for access to the best mobile ecosystem seems a pretty good deal to me, and I’m a mobile developer. I can agree that it seems expensive to Amazon or Spotify though.