I disagree, slayda, with the notion that there aren't any retail costs for e-books. Even if the Pub or Author, for that matter decides to sell the e-books themselves, they'll have to have some infrastructure to handle that. Even if they purchase pre-made e-commerce package and run it off-the-shelf, there'll be the cost of the package and hardware to run it on, and folks to keep it all running, etc.
Would it be greatly reduced? Surely, but it'd still be there.