Also, no matter how old or new a book is, you have the option of finding the pbook version used.
So with that arguement, the price of pbooks should drop after the first month or so. But then the used prices would go down, so the new book prices would have to drop.
So why not just give them away?
And no matter how old or new, as long as it is in copyright, you can't legally find the ebook used.
A good case for ebook prices to be lower. But until that happens, no matter how old or new a book is, if it is in copyright, the ebook and pbook (current printing) prices will be close.