I would of laughed at him if i was the Dealer, then politely tell him to leave the premises.
Just because the guy decided to pay $750,000 for it doesn't mean its worth that, i reckon in todays market he would be lucky to fetch $350,000- $400,000 IF it sells.
Its sad to say but he may as well throw it off a cliff if he needs the cash, because he'll get more from a insurance payout.