I have seen that dress sell many times on eBay and $100 does seem like the average going rate. I think your bidder got cold feet after winning. I think the bidder probably put in a huge bid to ensure a win, but didn't expect another bidder to go as high. The person who won your auction bid irresponsibly. Since the bidder did not follow through with the terms of the auction by paying in a timely manner, you have every right to leave a negative feedback saying you didn't recieve payment. I think other sellers need to be aware that this bidder has not followed through with the payment so they don't get burned too. I would also suggest reporting this to eBay, because if you don't you will have to pay final value fees on $100 even though you didn't actually get paid. As an ebay seller myself, I would recommend that you either check the feedback of your bidders or you can set perameters for bidders you will allow on your auctions. They will let you refuse certain bidder such as those with no feedback or negative feedback. As the seller, you also have the right to cancel bids that have been placed on your items. This might be useful if you see a person who has multiple negative feedback for not paying.

I don't think you will have any trouble selling this dress because it is retired and it seems like many people want it. You could relist it with a Buy it Now of $100 or best offer. You can also require that if a person buys it now that they pay immediately with paypal. That way you will be sure to get paid promptly.