It's very dependent on the style of the prom dress. They don't generally buy prom dresses unless they look more like homecoming dresses, so shorter than full length. The only way to really tell is to bring them in store if it won't inconvenience you too badly.
My granddaughter took two of hers there, one we paid around $400. for, the other over $700.00, they didn't want to give her enough for a meal at McDonald's so I brought them home and donated them. They were beautiful dresses at least some young lady got a nice dress for free
Depending on the season, you should be able to sell them, but it also depends on the store's policy.
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