There's a lovely story told by Danny Thompson (Pentangle, Richard Thompson, Sandy Denny, Nick Drake etc) of buying his first stand up bass.

In response to an advert, he went to find out more, and as a consequence, bought a reasonably priced double bass from an old guy.

The bass was painted black. Danny tied it on top of a car on the way back from a gig, and due to heavy rain, when he got the instrument home, the paint had washed off revealing a beatiful natural wood double bass. He investigated a bit and found that he'd got an instrument worth far more than the money he'd paid for it.

He went back to the old guy who'd sold it him, and explained the situation. The old guy simply responded: "I know what it's worth - but as you seem to want to play it so much, play it well - the original offer stands"

Ed

- Apologies if I've got any of the above details wrong, but the gist of the story is certainly correct