AUDIOBOOKS

Ok, so here's a question. Despite being a somewhat newly converted devotee of audiobooks, I've never bought one. Every audiobook I've ever listened to has been rented or borrowed from the library. My question is: Is there a difference between renting/borrowing and downloading the audiobook from the internet? I wouldn't have paid for it in either case and in both cases it has been bought once before, either by the person who uploaded it to the net or by the library/rental store.