Potential Market

How much would someone pay for a misshapen rock? My friend and her husband were at a lake near their home in St. Paul, Minnesota when she came across a rock that was shaped like a kidney. She has an online store in eBay, and decided to sell the rock. I was wondering who would gonna buy a stupid rock and I bet it will come up with zero bid. Well, I was wrong. Somebody paid $25 for the rock. That got my interest..... I was wondering what I could sell on eBay. I'm starting what I have of zero value that I could persuade someone to buy. One way to get richer is to come up with a product that is pretty much worthless, but convince people that it has some value. Whoever invented bottled water, that's a good example.