It’s easy. Thats what all the after-holiday price reductions are about. I buy a sweater for $20 and give it to you. You don’t like it so you take it back to the store without the receipt. The store has since reduced the price to $15 so they give you $15 back in store credit. You buy a couple of $5 t-shirts. Now the store has the $5 extra from the sweater, the sweater itself, and you will probably never use the extra store credit, and they made a profit on the shirts.
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(TITLE FROM REDDIT r/AdivceAnimals)