The Flatlander
A flatlander walks into a hardware store and asks for a chain saw that will cut 6 trees in one hour. The salesman recommends the top of the line model. The flatlander is suitably impressed, and buys it.
The next day he brings it back and says, "This chainsaw is defective. It would only cut down 1 tree and it took ALL DAY!"
The salesman takes the chain saw, starts it up to see what's wrong, and the flatlander says, "What's that noise?"