I do agree that text books containing quality material are worth their price, however, the quality of some books isn't there yet they still move plenty off the shelves.

In the software industry the best software for a specific function is generaly the most widely used(microsoft office for example). Who doesn't want the best performance and best features? From my college experience, this is not the case for the world of texbooks. I took 4 calculus classes and had to purchase 3 different calculus books, all of which contained the same material. Entry level calculus hasn't changed, so why does a book need to be updated every year? If someone wrote a book that provided excellent explanations there would be no need to update it yearly and it would be so widely there would be no need to make "revisions" just to sell more copies.

That's why we don't need revisions every couple years for the majority of books. Cutting edge technology books are one thing, but unless history is changing there's no need to write new editions of a 16th century European history book every year.