Ahh, hush money, the plot thickens. Option 1, take your expenses, postage, money order, etc. out of the $100.00, return the balance, leave feedback saying that he accepted payment and then sold the gear to someone else and held your money, then be prepared to fight the good fight if he leaves you negative feedback. Option 2, as Woody Allen said, "Take The Money And Run", perhaps the seller has learned the ethical error of his ways and needs a clean start. Option 3, same as option 2 except you send him the balance of the $100.00 back as in option 1. Option 1 would help to protect other members but you may find yourself in a protracted dispute. I would only keep the money only if I could do so with a clear consience. Zaikesman is ultimately correct, no sense in agonizing until the refund check clears your bank.