A quick note: All discussions of this event will draw commenters who think they magically know how books should be priced, and who say there is no reason for electronic editions to be more than $9.99. A quick note to them: You don’t know what you’re talking about. Seriously, your back-of-the-envelope calculations are crap. The printing costs of a book are generally between 3% and 10% of list price. So in most cases, 10% should be your “first-printing” e-book discount, not 50%. That may seem weird to you, but that’s because all the cheap stuff on the internet is backlist (like Baen Books), subsidized/coerced (like Amazon), self-published (no editing or marketing costs), or promotional (like when I gave Uglies away for free). Yes, the “long tail” of backlist books may become very cheap, or free, but not the new stuff, which is what this discussion is all about.

-http://scottwesterfeld.com/blog/?p=2138