I think a lot of people here are underestimating the expense and difficulty involved for a publisher to convert a book that they do not already have an accurate digital copy for into an e-book. Right now I am finishing up converting a used paperback book into an epub file for my personal use and I can tell you the process will ultimately have involved about 40 – 60 hours of work. That is to get a work that matches the original text and is in a nice format for my reader. I should mention that this is a book of about 200 pages; a cost per page model is appropriate here. Sure the publishers could not pay for all that effort for proofing the OCR output from scan and be able to sell it for a relatively cheap price, but that's all it would be worth. And this assumes that the publisher already has rights to publish as an e-book without having to go back and negotiate for these rights with the author or copyright holder.