Back in the early eBay days when it was primarily an auction site I once sold an OOP Folkwear pattern for over $100/£72. I was shocked someone would pay that much for it.
I have, in the past given or sold dirt cheap my Issy miyake patterns (you may have bought one from me) thinking I would never use them again and now I see the same patterns going for £50+ on eBay. How I regret getting rid of them.