That does seem a bit high but I wouldn't say that it's impossible. If someone is going to spend hundreds on a device that's meant soley for reading, they probably read a lot of books.

Anecdotally, I just got an iPad and bought 3 books I've been meaning to read for a while. Before that, I hadn't bought a book in months. In a way it's like the app store but for books - looking for and buying a book was so easy that I'll probably buy more than if I had to go to the store every time.