One of my teacher has a slight accent. This can be humorous for the rest of us.
Teacher: "Some goods are cheap; others are being expensive. The price of air is for free. But how much is the price of aisle?"
Students: "Um... What?"
Teacher: "Aisle. What do you have to pay to get some aisle?"
Students: "We don't know!"
Teacher: "Aisle costs seventy dollars a barrel!"