This is kinda why people pirate books to begin with. Ebooks are great and all but are, for the most part, too expensive for what you are receiving. Most paperback books cost around $7-10. The ebooks of these books should be no more than $4. Why? There are no printing costs, there are no distribution, inventory, or other costs, so why do many ebooks cost as much as the full paperback version. I will refuse to pay any more than $4 for an ebook (read it from the library, etc). (Not to mention the DRM). The author will have lost a paying customer.
If you charge a fair price for your books people will buy them.
In my opinion: Typical paperback costs $8.99. Ebook should cost only $4. (the same amount of money goes to the author--publisher--You aren't printing anything so yes, you should be making less).