As I was thinking about your question, I realized it really is very situational for me. Manga, for example, is my first love when it comes to books, comprising over half my library. I'll plop down the full cover price of $9-11 each for one, minus my B&N discount or the usual Amazon discount if it is a series I'm really loving. However, I also remember when one company started up releasing stuff and their volumes were $13 each. I wouldn't buy them at full price at all, no matter how much the story appealed to me. There was also one manga series I love, D.N.Angel that I have continued to avoid buying the most recently released volume of. The price was the same, but the volume was so thin compared to the rest, that I couldn't justify the price. I'm the same with light novels, happily paying $12 a pop for them.
When regular novels, though, I seem to swing the total opposite! I rarely, if ever, pay full cover price for a novel, non-fiction work, or any other non-manga/non-light novel. The bulk I get at Half Price books for half price (da dum dum), or I'll pick up in auctions, at Wal-mart, or at some heavy discount bookstore. Unless, it is something I've long been seeking or really really really want to read. Albert Payson Terhune dog books, for example, I'll pay up to $50 a pop for in eBay auctions for early editions, versus paying the maybe $8 for a modern reprint. Paid $30 for a rare copy of the Fox and the Hound (finding the author's signature in it made it a bonus - you may hate me! ***mwua ha ha***). Looking at some of my recent purchases....I wanted to try Allison Brennan's new Seven Deadly Sins series. Half Price had the second book, so I paid full price for the first one at Barnes and Noble, then got the second half price. If Half Price didn't have it, I probably would have grabbed it at B&N as well. So its not so much that I think most regular novels aren't worth the paperback cover price, but being, uh, thrifty.
As for eBooks, I honestly won't pay for them at all. I don't have an eBook reader, just the Kindle for PC and I will only read the freebie ones or ones I borrow from other folks. I don't read most "real" books there, though. Almost all are eBook only releases. If it is available in print, I'll try to get it from the library if I want to read before buying. If I can't get it there, I'll try to borrow on eBook, or just go without. I think I have only ever actually deliberately bought one "eBook", which I bought before they actually became big. It was for a game guide that was out of print but offered by the company as a downloadable eBook. I think its stuck somewhere on my desktop that has been out of commission for two years now...paid $10 for it, but wouldn't do it again.