Look at this e-store :
www.eons.fr
It's in french but just check the price they ask for their pbooks and ebooks,
they sell both and their ebooks (with DRM) are about 1/3 the price of pbooks.
So most of their ebooks are only 2-4€ (with a few exceptions).
The truth is that currently publishers don't believe in ebooks and don't care
asking such a crazy price. Servers are NOT expensive, including DRM is
not so expensive and creating an ebook is not difficult since the publisher
already has an electronic version of every books.