Not if they raise it everywhere to cover it. This is exactly how Apple's policy can raise prices for end users.

Competitors without apps will not raise their prices, though.

No, YT simply charges a higher subscription fee if you do it through the Apple in app purchase.

Is it really against apple's ToS to increase in-app prices to make up for the 30% fee?

It was part of a set of changes that were meant to go into effect in July but that Apple rolled back. You're allowed to charge a different price but you can't tell the user that they can get it cheaper elsewhere or that you're paying 30% to Apple.