> If you are shocked that companies take a fee for distribution then wait until you see how things work in the real world.
That is not a good analogy. Supermarkets, retailers etc charge a fee from the vendor because that is their primary source of income ("bread and butter", if you may). In the OP's case, the "supermarket" is an iPhone device which the user has already paid a premium price for.
Depends on how you define "allowed". EA was "allowed" to charge extra money for unlocking key Star Wars characters even after you paid in full for Battlefront II. So, the idea is less about what is "allowed", but rather where the line is drawn between justified commercial profit and monopolistic/bad behavior*
> Grocery stores also have slotting fees.
Again, the whole point I'm trying to make here is that comparison to grocery stores just doesn't work (because of reasons mentioned in the first comment)
* English is not my first language so I'm having trouble finding the perfect word.
> You don't have a choice to distribute iPhone software.
Just broaden the market to software in general or even just software for mobile phones and tablets. Then you have a choice again. iOS's market share is below 50% even in the US, and much lower globally.
(I have both iOS and Android devices, and I specifically like that Android's Firefox allows add-ons like uBlock Origin. Apples doesn't allow those.)
And I am perfectly aware that the situation was even worse before the App Store.
In fact, by all means, Apple created a viable ecosystem for a huge number of independant developers and that's great.
Still, 30% is not justified, and this is not Apple hate, Google and Valve are on the same boat.