It's not just that, it's the obligatory equal pricing, so you've no way to pass Apple's 30% on to the consumer. It's a cost that businesses must be able to swallow if they want to play inside Apple's ecosystem. They now have to exclude themselves from the biggest selling mobile OS (yes, I'm counting iPod Touches and I do know that Android phones outsell the iPhone) or find a way to supply 30% to Apple while still being competitive with those that have excluded themselves from iOS.
For someone like Netflix, Spotify, etc consider US$99/year to supply a free iOS app to their subscribers versus US$99/year + 30% of take from anyone that creates or renews their subscription inside the app, with no option but to add that functionality to the app. And it's for subscription services, so you're probably not getting additional revenue from the on-average more affluent iOS customers versus customers in general, and Apple's rules prohibit a different price for iOS customers.
Likely outcomes are (i) dump iOS; (ii) introduce a higher subscription rate for all mobile customers. And the latter just adds weight to any consideration of the former further down the line.
On the flip side there are people, like my own company, with no previous subscription infrastructure in place and aspirations. This is great news for us, but for the industry as a whole it's likely to turn iOS into amateur hour. So even we're seriously considering whether to do anything.