Hi Simon,
eBooks are almost always slightly cheaper than paper books from what I've seen, maybe 10 - 20%. This is due to the elimination of physical print cost, which typically amounts to that proportion (although many people tend to have the impression that physical print cost constitutes most of the book's cost).
There are numerous eBooks on Amazon that are $9.99, but only because Amazon is forcing the publishers (especially smaller ones at their mercy) to sell at a much lower margin, which many believe is not sustainable. Then again, it all depends on how the market plays out, now with Apple and Google's bookstores becoming major competitors.
And yes, there are certainly other routes to these books. Quick and easily accessible routes via the information superhighway. So whichever e-reader you purchase, you're never limited to the official channels.
