Facebook is objecting to allowing people to know that they're being tracked everywhere by them. Lots of people don't really understand how that works. I think this is a good thing Apple is doing in this particular case.
It absolutely is hidden. Apps are not allowed to be transparent with the user, for how much money is being taken by Apple, directly in the app purchase screen.
That is against the app store TOS, to show as a line item, the cost of the Apple cut.
are you sure about this? "Apple blocks Facebook update that called out 30-percent App Store ‘tax’" [https://news.ycombinator.com/item?id=24301332]
disclaimer: I work for fb
Does any of this make you want to reconsider that?
If I were marketing to youths, I'd have to deal with Apple's 90% market share among my customers!
In this particular case I don't care because FB is garbage IMO but the point stands - Apple has too much power in the US and we need to force them to allow third party app stores.