To me, the flaw in this logic is that is explains how the pie is cut up without ever discussing how big the pie needs to be. Should a publisher expect that the sale of an ebook will net them the exact same profit that a print book will? I would argue no, because the production model is essentially different. With print books, publishers need to print the book in order to sell it, and once that book exists, the owner can resell it easily. As others have pointed out, the web makes selling used print books easy to do, allowing used books to compete with new books. On the other hand, if the publisher wants to sell more new copies, they have to print more copies. With ebooks, the publisher does the initial set up once and then sells as many copies as the market will bear. And the 3-5% DRM charge mentioned above makes it much more difficult for an ebook's owner to sell his or her copy to someone else after it is read.
Just as the web changed the way we do business, I think ebooks will eventually change the way publishers sell books, once publishers figure out what profit they should expect from an e-book. The wireless feature on my Kindle is great, but one reason I love it so much is Amazon had the smarts to provide a free "taste" with most books in the Kindle store. This try-before-you-buy feature is fantastic! In the long run, I buy more books because of it.
Which is not to say that the change won't be slow and painful. Evolution so often is.