I don't think they even report out on the profitability of individual apps. In fact, I don't think they report on software profitability at all: the categories they report out on are Mac, iPhone, iPad, Wearables, and Services.

No one outside of Apple has any real visibility into how "profitable" any individual app they make is, so I can't imagine this is a factor in why they don't charge themselves the 30% cut. In fact, I don't think there's even any way for us to know if they do—or if there would be any meaning to it if they did (ie, would the 30% even go to a different internal account?).

Right, but that's something any audit will poke right through, and if you take the paper trail (or follow the money) far enough, it just ends up with whatever tax haven corp that is used for the money either way, and the profits and losses still end up with a net zero difference.

Technically, it doesn't even matter where this split is made, if you go up the tree high enough, it merges and just cancels itself out.

What apps does Apple charge for?

TV I guess?