Value based pricing. The value of an e-book is close to the value of a p-book to the user. The details make it a wash depending on who you are.
Some people might want to sell the p-book when they are done, but you may be able to make copies of the e-book.
Some people like having the p-book, other people have too many books and clutter already and like to read technical stuff on a tablet while spinning at the gym...
There is plenty of other pathology in book pricing.
Allegedly hardcovers are worth more than softcovers but most of the time a used hardcover is cheaper than the softcover because: (i) softcovers are often nicer objects to live with, and (ii) libraries and their patrons mark up and otherwise abuse hardcovers.
