Nice idea, but how much??!
I think the opening comment completely misses the point on cost.
The cost of the device itself has never been as huge a problem as the cost of every e-book purchased. Most e-books I've ever looked at sell for around the same or even MORE than the physical books. However they have no re-sale value (thanks, DRM), and they cost absolutely nothing to produce and distribute, so why does the cost not come down?
Yes, electronic format is cool, and it is nice to have 20,000 books in one device, but most people only read ONE book at a time! It's not like MP3s, where most people like to listen to many tracks in one day, hence electronic format is far more convenient and there doesn't need to be a price advantage. Books however is a completely different product and these readers will never take off until e-books are substantially cheaper.