The argument here is that if you want to produce an app for iOS you have to provide it through the App Store and thus succumb to the 30% fee. The same applies if you're using Apples payment processing, which you actually have to use if you want to offer any in-app purchases on iOS. In addition Apple is the sole authority on what is and is not allowed on their storefront. If they deem your app is not acceptable, you have no alternative ways to distribute it to users. They can also kick you out if they think it's necessary, again leaving you with no alternatives.

Google does the same thing with Play Store. If you sell an app in Play Store, Google takes 30%. If you use Goolges payment processing, Google takes 30%. They can kick you out, not permit you in the store, etc. The difference is that a developer isn't forced to use the play Store or Googles payment processing.

You can distribute your APK in any way you want to and users can install any APK from any location they want to. You can absolutely sell your Android games on your own website and just provide an APK to a paying user and now you don't have to pay 30% out of every purchase. If you want to provide in-app purchases the user can provide their CC information and you're free to process the payment in any way you want to, again, circumventing Goolges cut.

This is the primary reason you can't get Fortnite from the play store, instead you have to download an install an APK. Epic also uses their own payment processing systems, so they don't need to pay anything to Google for IAPs. They can't do that on their iOS apps, meaning they're losing on some hefty profits simply because no alternative exists.

So it's not that Apple is jacking up the profits, rather you could say that you need to pay a hefty tax to provide your app to iOS users.