It will all sort itself out in the end - supply and demand. If we aren't buying the price will come down to a point where we are prepared to buy. Just look at how much a DVD comes down in price even a few months after its release. Okay, so there is no physical stock to contend with but the principal is the same - the price will always be set to meet the demand.
Frankly I think $10.00 is too much to pay for most e-books. The only cost the publisher has is what they pay the author and editor, which is typically 10% of the selling price. If you assume that an author is going to want $2.50 per book (10% of a $25 cover price) then if the publisher were to charge $5.00 per e-book they would still be making close to $2.00 per volume (subtracting out advertising costs).
This is a case of trying to get whatever the market will bear. Ultimately they will be able to get the big bucks for popular authors, but they are seriously on crack if they expect to get $15.00 for little known/obscure books.