— Girl Math: Returning an item means that you're making money.
This is an example of mental accounting.
When we return an item that we have already purchased, it feels as if we are making money. This is because of mental accounting, a term coined by Richard Thaler, which describes how people think about money relatively rather than in absolute terms. According to mental accounting, we view money differently depending on its intended purpose. In this case, the money that was spent was intended for the item that was already purchased, so when the item is returned, there is a disconnect in our brain, making it feel like we are gaining something.