That a dealer, or anyone at an auction, would spend $25k for a 1988 coupe is beyond belief, he must have been bidding for a private party, and maybe one that knew something special about that car. (A pound of blow hidden in the gas tank).
Yes, it's still a desirable car, but they sold plenty of them and they are widely available in good condition for that price or quite a bit less. Out of curiousity, how much was a '99 996 coupe going for?