I was alerted, here, to that trick, long before I 'Bayed.
When I wanted a swish remote I spent a lot of time bidding light and ventured to near the selling price once. Sure enough a stranger had the same kind of device and would sell it at my bid price. He offered for to let me pick it up in central London. Yea - right! I suggested he put it on E-bay and he would get a better price, and if I didn't see it there I would figure my assumption was correct. It didn't appear.
When you have a purchase record of zilch they assume you are not street wise. Without the Mudcat that could have been the case.
One way to fob them off is to claim you only deal through PayPal. & offer to pay the extra for the guarrantee service. If they are genuine they will still deal.