It's also not a bad idea to just go through the eBay dispute even if you agree with the seller... essentially it just keeps a solid record of the transaction and I think you may get back the fees of the refunded difference; but I'm not positive about that part.
Oh, and I assume there is no way to know for sure if that is your base or not... probably not individually numbered? But I would not put it past someone to swap out a broken item in order to save money. And I'd check the buyers buying and feedback history just on the office chance he has purchased a broken IM statue or has left a lot of neutral and negative feedback when people didn't agree to refunds... there are a number of people who just scam as much as possible on eBay and you really can't tell until you do some digging.
I had that happen when I sold a used ipod years ago, the guy said it was broken and wanted a full refund and to return the item. I knew it was functional when I sent it and didn't believe it could have had any damage. So I check his buying and selling history and sure enough he had left a lot of neutral and negative feedback for other sellers and had bought and sold a number of broken ipods. I submitted my findings to eBay and they sided with me, I kept my money and the buyer got nothing but to keep what he paid for.