For the pbooks I own and refer to often I would gladly pay $2 - $5 a book to get them in a ebook format. For books some I would pay much more than the pbook cost to get them as an ebook but alas no-one has digitised them yet.
At the moment I hold onto all my pbooks because sometimes it is easier to grab them off the bookshelf rather than find and load the file on my computer. And with textbooks I sometimes need to refer to two or three books at once and I can't afford to buy that many ebook readers

(I know I could 'ALT-TAB' between ebooks or whatever but that's too slow sometimes).