This doesn't add to the debate and detracts from it. To come back to it - we were not discussing whether it is fair for Apple to charge how much ever percentage it does on its app store vs Amazon (or anyone similar).
The crux of the matter is that neither Amazon or Walmart or any other online or offline supermarket restricts anyone from buying a product directly from the producer / manufacture or from elsewhere.
Apple does precisely that with its app store on ios (and soon will on macOS too). By depriving us the freedom of buying from the developer (or others) directly, Apple not only violates our privacy but also raises the cost of an app for everyone (by unnecessarily charging the developer an annual recurring fee and by charging a commission on sale).