How come when I go buy something at a garage sale for $3 it turns out to be worth a buck and a half?

So, there story goes like this: this guy goes to a "red tag" sale and buys a bowl for $3. Then, for some reason, he gets curious about the origins of the bowl. Well, as only happens to other people, it turns out to be a very rare bowl from the Song Dynasty.

Hmmm. Why do I doubt this story? Something doesn't fit.

Fast forward to Sotheby's auction where the experts say it should bring between $200,000 and $300,000 at auction. Turns out the "experts" were off by a few bucks. The bowl went for $2.2 million. Not bad for a $3 investment.

I'm still a bit cynical about this whole story. I just find it odd that anyone would suddenly get all curious about a $3 bowl that had been sitting around the house for a couple of years. Then, when taken to Sotheby's, the experts there are off it's estimated price by $2 million dollars.Really?

It's not like the folks at Sotheby's are just taking a shot in the dark when the estimate these things.

I could be wrong. I think there may be more to this story.