I don't agree that the price of an ebook should the price of a new or used book minus the resale value.
1. many people like myself actually keep the text book because the point is not getting a good grade...the point is learning. and keeping the book is better for long term learning.
2. the electronic version is inherently better. u can do a search. u can save portions of the text and save them for later. u have it with u everywhere. lighter. takes up less space. eternal storage.
thus, I think they could price these ebooks at slightly below the used price.
from the publisher's perspective ebooks should greatly increase profits because
1. remove used book market....lose massive amounts of money
2. no cost of printing.
3. no logistics and storage costs
4. makes piracy harder....depending on DRM effectiveness.