how do car rental companies make money?

[Professor]

Their business models are like Blockbuster back in the day. Blockbuster didn't make a lot of money on rentals. They made a lot on late fees.

Rental companies make a lot of money renting during peak times. But, most of the time, they make money buy selling you insurance that you already have (most auto policies extend to a rental car), charging you $9/gallon if you don't fill it up when you return it, charging you $100 for a GPS rental, etc.