Not only are they expensive, they are also not sold. They are licensed. This removes the ability to use the provisions of the first sale doctrine. So you can buy a license to a book - but you can't transfer it. With a physical book I can sell it to a used book store, hand it to my wife or kids and let them read it, send it off to a friend in another state, donate it, etc. With an e-book I can't (legally) do any of that. I can't even let my wife read it on her e-reader (separate account). Since we are very limited in what we can do (again legally) with them, they don't have the same value to me as a consumer. Yet they charge the same (or higher) price. I had put my thoughts on this into a blog entry some months back. They still pertain now. http://gildude.blogspot.com/2012/03/have-you-bought-into-e-book-model.html
One of the things I'd like to see if the ability to transfer from one cloud service to another. Amazon has theirs, Google has theirs, other folks likewise have theirs. But I have no (legal) way to transfer an e-book out of say Amazon's service and into say Google's service if, for instance, I decide I want to use a different e-reader and move "my" licensed content. Can't do it. The only value I get out of e-books that is missing from physical books is the amount of books that can be stored on a small device and the ability to add more to that device from say a hotel room on a trip. However e-books have all the previously mentioned downsides - many of which people are very slowly becoming aware of.