But what's happening is that this 30% is more or less a lock-in cost for the only official way to do business on IOS. And before this ruling, you weren't even allowed to mention in the app that consumers can also pay on your website. And now we come to this article saying "okay, you can show your website were still going to charge you 90% of our rate despite handling none of those transactions". And that's where things get really dicey.
With this new perspective, the question shifts to "is apple's 27% for distribution (minus payment processing) reasonable?" and I'm less sure. Especially when Apple can throw out my app for any reason whatsoever.
To use android for comparison, I can throw an APK up to download with relatively minimal effort, with zero regards for Google's rules and I owe Google 0% of my revenue. They still take 30% for using Google play as distribution. But it's nice knowing I could theoretically host it elsewhere if I don't agree with Google's pricing (minus some bribing issues Google is currently being taken to court for). There's none of that for Apple. Firefox is just a Safari skin because Apple says so. Emulator apps are in flux based on Apple's whims. Your app may be taken down for nudity as Apple profits millions from a few dozen games that barely try to hide it.