I'm certainly no expert, but I've sold chips on ebay for years.

I think it would depend on the seller's return policy. When I sell, I give an unconditional guarantee...no reason needed. A happy customer being the most important to me. However....

As far as legality goes...I would think that if the chips was offered for $1200. and someone agreed to buy it for that price, you have a done deal. The buyer should have been sure of the price he was willing to pay prior to the purchase.
Shop around, make your best deal.