Joshua Bell, Free and Clear
An interesting story. And the Snopes commentary is also interesting.
For my own part, I know I can tell the difference between a $3 bottle of wine and a $10 bottle of wine, but I have very little chance of distinguishing a $15 bottle of wine from a $70 bottle of wine.
And I usually stop to listen to musicians in the subway, and leave a buck. Perhaps because I can't tell the difference.
(Nod to the LMM)