But will this be true for long, now that this particular shoe has dropped?
Apple's primary target here is probably Amazon. A company which, incidentally, is no stranger to the art of using a powerful distribution network, an existing customer base, and a DRM-locked e-reader platform as a lever to demand big shares of revenue:
http://www.jeremyrossmedia.com/2010/02/21/word-kindle-70-30-...
According to this article, and the Stross piece linked therein, Amazon's standard deal is that they take seventy percent. Their "generous" deal for self-publishers is that they take a mere 30%... but the publisher must give Amazon the right to set the price as Amazon sees fit.
Makes Apple's 30% cut look pretty good, actually. But, of course, if you're a print publisher you pretty much have to have a deal with Amazon, so I expect there are a lot of negotiations going on right now.