The Washington Post gives front page coverage to the high cost of textbooks and what can be done about it
link here. It notes that Congress passed a bill "forcing publishers to release more information about their prices. It also requires them to sell a textbook separately rather than packaged with a CD or workbook that makes for a more expensive purchase. However, the provisions do not take effect until 2010." Several states have passed similar laws as well.
The article goes on to note the thriving used textbook market but observes that prices are very close to those of a new text. Some teachers are also encouraging used texts by not changing them from year to year. Finally, the authors note the existence of a thriving exchange for scanned copies link here using a disclaimer that the site is not responsible for text illegally copied, since all users sign an agreement that are the original owner or abide by the copyright laws.
The article fails to mention the legal downloading of texts available on the internet where the author has put them under open license.
With the ability to use computer technology to produce books thereby reducing the expense of human involvement, one would think that the cost of books would go down. You can scan images, so you don't need to have a graphic artist generate art work from scratch. Spell check minimizes the need for editors. To update the book, you don't have to re-write everything. All that I can assume is that "market forces" are not being allowed function in order to promote competition in the text book market.