A search of Autotrader will only show that people thinking they are gonna get nice SNs for $4k and down are dreaming.
NADA value on a '98 GT coupe with 80k miles with leather/Mach is $7,575, as of today. I'd be leery of anyone selling their car for significantly less than that. Most dealers are selling for much higher than that. Anyone thinking they are going to get a nice GT for $2k is not going to get one. Maybe a 150k mile beater, but nothing very nice.
I don't know where people supposedly find these cars for less than $4k for a NICE one (not just a "clean" one with Lazer Pink paint or peeling clearcoat and stained interiors), but they certainly haven't been on Autotrader/ebay in the last six months I've been looking. Trade in ranges between $4k-$5,500 right now:
http://www.nadaguides.com/Cars/1998/Ford/MUSTANG-V8-5-Spd-AT/Coupe-2D-GT
So, based on the NADA retail value, since that's what insurance will pay out in an accident, if you can get a beautiful stocker for around that price, then you've done well IMO. Most dealers are asking north of clean retail, by quite a lot, so if you can wiggle down to retail and it's the right car, then snap it up.