Illegal based on what? I don't think asking someone a commission is illegal, and I doubt the high percentage is illegal as well. And neither is the requirement that in-app is available for the same price as when you subscribe outside of the eco-system. Lots of retail pricing in the world is done that way.Good! This new subscription program by Apple is completely illegal.
If companies don't want to play Apple's game, they can move on to other platforms. Same as that some companies only make Wii games, and others XBox games or PS3 games.
And if Apple thinks they will loose too much market share by companies refusing the provide applications to their eco-system, they can lower their commission rates if they want to. Or they can be just stubborn and do nothing.
Said that, you may not like it and disagree with Apple's percentages or requirements. But I doubt it is illegal. It's not that there aren't alternatives, or that Apple is using their weight to push others out of the market. Because only then monopolies are illegal. It's not illegal to be the only one providing a product. It's illegal to prevent competition. None of which applies to Apple.