$150.00 is not really fair...
Actually

,
In all fairness, the store owner should be told he's selling a $50,000 item for a buck- fifty" as he has overhead, a wife to please and tennis shoes to buy for the children.....
Then, if all's fair and just in the world, the thrift shop owner should inform the widow that she dropped off a very valuable JBL treasure because she shouldnt be penalized for her ignorance after all she has bills to pay too................