Seriously, how much do do think materials and production add to the cost of a book? Look, you can get a good laser printer that will do a double sided page for $.05 and one double sided 8.5x11 is roughly equal to 4 pages of a hard cover book. So with consumer equipment you can print the equivalent of a 400 page book for about $5.
I'm not a publisher, but I've got to believe that they can do it cheaper than I can with a printer from Staples.
So ever with a nice hard cover and shipping and handling and everything the entire physical costs of a book are under $10. Probably under $5. And that's roughly in line with how much cheaper e-books are than new hardcovers.
The rest is profit, aka how the writer and publisher feed themselves. And publishing is an industry that is famous for how much money everyone doesn't make on average, so don't whine about them ripping you off.
The publishers need to do a better job of lowering prices as time passes and on older books. But this "digital should be basically free" meme is bullshit.