Sorry to hear of your problem. I just bought a N810 for my husband off eBay on Saturday and he got it yesterday in great shape. The back had a few minor scratches but I know from my own N810 that the back scratches very easily - so no big deal in my mind. The rest of the body & screen is pristine. We paid $363 including shipping. So I guess you never know...

As for your refund $$ issue - if you paid with PayPal and the guy has > 50 feedback (if he's a powerseller he will) and if the majority of that feedback is positive then PayPal says they will cover your purchase up to $2000 when the item you receive is significantly different from the ad. I would start there if it were me. PayPal can put a hold on the seller's fund in the case of a dispute, if the seller has any funds in their PayPal account.

I really hope this all works out for you. eBay can be an excellent place to buy items.