Each year, children collect their trick-or-treat goodies and then go about trading their candy with each other. This scene from a 2019 Walmart commercial illustrates the concepts of gains from trade, bartering, and mutually beneficial transactions. Each child only trades an amount they are willing to give up and aren’t forced to trade with each other. After the exchange, both are better off than they were before the meeting.
Thanks to Brian Lynch for the recommendation!