We bought this ashtray dirt cheap. We had no plans to sell it. Someone made an offer, and we refused. They made more offers, and we finally caved in and sold it for $500. I've regretted it ever since, because we've never seen another one.

I bought this keychain on eBay. An torn, empty envelope arrived. I've never seen another one

Hypothetically, if my normal price max was $20 for something...I'd raise it to at least $30 for a great item I'd never seen before. The love would win, until the price was sky-high.