As a developer (though it has been a few years since I wrote code for mobile) Apple's tools, documentation and libraries were so much better than Google's, though that may say more about Google than Apple. And I approve of app store revenue supporting those tools.
But 30% is really, really high. I don't work for Apple, or Google for that matter, so I have no insight into what portion of the money goes to the services mentioned above, but it seems to me that even 20% would be pretty hard to swallow, and 30% seems unreasonable.
I would love to hear from someone with actual knowledge of this how much of that app store revenue is profit.