A long while back I worked for University of Texas @ Austin's bookstore. Those text book prices are such bullshit. I can tell you that the publishers will do things like just rearrange a few paragraphs or chapters and change some pictures without adding real new content and boom, new additions, higher prices. Also, they're known to make deals with some professors to assign their text books only in return for some kickbacks. I've had a few professors that were understanding and would make sure the book was available to borrow and copy in the library or that it was available used. I don't miss that part of going to school. Especially when you can't sell them back. -_- 

Working on a post, hope to have it up shortly...ish.