The shopkeeper picks one out and says “this one can cut down 5 trees in 2 minutes”. The lumberjack is impressed by this and buys the chainsaw. 2 days later, the lumberjack comes back to the shop with the chainsaw and asks for a refund.
“This is a complete rip-off, I only managed to cut down 1 tree over the space of an hour!”
The shopkeeper takes the chainsaw and turns it on only for the lumberjack to suddenly jump in surprise.
“What’s that noise?”