Ebooks 50% off of Textbook version, but expire in 180 days.

[primbs]

Here is one way a company is cutting prices on ebooks vs. printed books.

"eBook and individual chapters are PDF equivalents of the printed text. They are functionally equivalent to the printed version but in some cases, individual items have been removed for Web delivery due to rights restrictions.
The eBook does not include any assets or study materials that may come free with a printed textbook."

"Standard length of access for eBooks and eChapters is 180 days, with the exception of textbooks designed for two or three semester courses. The amount of time remaining is noted next to your title within MyStuff. Once your content access expires, you can re-purchase access by coming back to MyStuff and clicking the "renew" button next to your title."

http://www.ichapters.com/market/index.html