A speculative trader heard a rumour that sardines were going to be in short supply, so he bought a large consignment of tinned sardines.
As the price went up they changed hands several times, and each time the seller made a good profit.
One day the current owner of the shipment was hungry, so he opened a tin and helped himself.
He immediately became violently ill.
He complained to the seller, who replied, “It is your own fault. Those sardines are for trading, not for eating.”