This is a beautiful quote because it is an example of one industry's bad behavior leading to another industry's bad behavior, upon which the first industry then users the second's similarity to justify themselves. Cars only started doing this because phones made it normal. It's wrong in both cases.
It's similar to when Apple defended it's 30% store cut by claiming it's an "industry standard"... specifically, an industry standard that Apple established.
A sibling comment notes that Steam charged 30% at the time (though some had better deals) but it's worth noting that Steam was not an open platform that anyone could publish on. Much like for consoles, to put a game on Steam you had to have a preexisting relationship with Valve, or try to develop one with no certainty of success. This was also considered a very generous cut because getting on Steam was almost a guarantee of financial success.
No, it wasn't. I'm not going to dig up links, but one could pop a web site storefront and Fastspring for payment processing (as one example of a company I used) for less than 10% (Fastspring would take something like 6-7%, IIRC). Discovery has always sucked on Apple's store, so no value-add there. In fact, I'd argue that the only value-add one gets out of Apple's store is access to their closed garden.
And "50-90%"? Is that in reference to putting software in physical boxes and on CompUSA shelves? Because no mobile publisher charged 90% before Apple's store came along.