Yeah, my stance has always been that companies should exist to:
1. deliver value.
2. capture a fraction of that value.
I think it is pretty clear in most cases that 30% is well above the value Apple is actually delivering with their App Store. It's not like Apple is building the apps for other people. You still have to build the app entirely on your own, the only thing Apple is doing is letting you distribute your app / distributing it for you, which costs pennies. People keep saying "but you wouldn't have devices to distribute your app to without Apple" and while that is true, Apple is already capturing the value for that part of the deal – they're selling the devices to customers. If they were giving away iPhones for free, that would be one thing. But if the only reason you are able to charge 30% is because you've monopolized distribution on a device that the user "owns", that is not ok.
Then there is the dubious value Apple claims to be providing to end-users by "maintaining the quality of the app store", but I don't think this is true anymore. Shit-tier apps get thru every day, and great apps get knocked for arbitrary reasons. Apps are pretty well sandboxed at this point, requiring explicit permission for most worrying features, so I don't really think Apple oversight is needed. Allow 3rd party app stores already.