The costumer buys the shoes
A costumer has to do with someone who makes or wears costumes, not a customer who is buying something (emptor being 'buyer', 'purchaser' which doesn't necessarily have anything to do with costumes).
Thank you for the explanation!
By the way, there are a lot of people who are making this mistake and reporting their answer as "correct." Everyone reading, please double-check that you haven't made this common error before reporting! Thanks!