Why are ebooks so expensive?

The other day, I wrote that I got a Nook. One of the perks I thought I'd get was access to cheaper books in e-form, but it doesn't look that way. For instance, the Nook book version of How Language Works is 17 dollars, and the print version is 18 dollars. If it costs so much to print books, then why is it only one dollar cheaper to get the electronic version? Some ebooks are cheaper, but some publishers are not being realistic when selling various versions of their books. Even with the occasional coupon I get from Barnes & Noble, it still doesn't bring the price down to an acceptable level. So I'm not going to buy it, and probably other readers see the illogical approach to such book pricing, too. Pricing e- and print books similarly isn't justifiable.