Pareto Parking

We parked our car at the Austin airport for six days, and my brother then picked it up to use during his three-day visit to my mother. He left it in airport parkinglot when he flew off three days later, a few hours before we returned.
This exchange was a clear Pareto improvement: he avoided the cost of renting a car, but he saved me three days of charges for parking ($30). I can’t think of anyone who was made worse off by this exchange, and both of us were made better off. My mother commented how altruistic I was to let him use the car; but, as is so often the case, my motive might just as well have been pure selfishness.