30% is insane, but lets keep the number aside for a moment.
If the user chose app A over app B then specifically what help has Apple provided to the App creator of A to justify the 30%? Apple's argument is they're bringing customers. But even if they do nothing one App is going to get the customer anyway. Also, Apple gets paid for advertising Apps and services to end users, so again, what are they doing to bring in customers to specific apps?
>what are they doing to bring in customers to specific apps?
They are making all the devices your app runs on. They are putting your app in their app store. They could remove your app from the app store and 0 customers would come to your app.
I don't know. I have released 0 apps and own 0 apple devices. I have never used their app store, so I do not have enough information to answer. I believe that question is irrelevant because apple is providing you a platform regardless about what apps they try to get people to install.
Everybody and everything can "provide a platform" if you do enough mental gymnastics. The AWS infrastructure you do you business on 'provides a platform'. The networking devices that route customer traffic 'provide a platform', the browser API 'provides a platform', the CPU that you code runs on also 'provides a platform'. "Providing a platform" doesn't entitle someone to grab 30% of sales from a business. If I rent office space, I pay the rent which is a mostly fixed amount, I don't pay them 30% of sales from my business - Yes, not a perfect analogy, but you get the point! Grabbing 30% of sales is just unethical, but that is just my view.
Which is why they take a 30% cut.