You're looking at it from a, "Give them a razor and sell them the blades." approach, but unlike developing an electronic reader with wireless connection, razors are pretty cheap. And another problem is the market for electronic books has not grown enough and there are few players in the game (Sony, eReader, Kindle, Google and soon Apple). The competition is going to pick up with Apple and the iPad.
Amazon is trying to expand the market and gain control by offering as many book titles as possible. They do not want a public perception that there are popular titles that are unavailable, so they pay the publisher in order to sell a book for $10. Why buy a Kindle if you run the risk of not being able to get the next best seller?
Now if you can get a Kindle for next to nothing (Like the Kindle on PC which is free) you may not be as concerned with trying to recoup your upfront investment in the device by getting all titles at a discount compared to the paper version.
I use the eReader (free software) on a Windows Pocket PC phone. These phones, like the iPhone are not cheap even if you get the 2 yr data plan contract.
I have no clue where this market is going, Amazon is trying like hell to be there.