If you go looking on the internet for a book you're trying to sell, you'll often find it out of stock on Amazon at 30p even when the next cheapest bookseller (who will likely have it in stock) has it at £112. I miss out Amazon's prices on books when I'm pricing stuff I'm selling for just this reason.

I think Amazon just leave the information lying around as a "spoiler" to stop people buying books at the right price (or to make them dissatisfied with the product someone else is selling).

:-)
Ian