You can definately find a '91-'92 turbo between 6k and 7k. I've seen 2 or 3 for sale RECENTLY on the MR2 board, with decent mileage (around 100k). It's definately not impossible. You just gotta keep your eyes open.
I paid $2300 for my '91 turbo w/ 128k on it. Just needed a little fixin up. But definately worth it in the long run!
Keep your eyes peeled, and if you don't mind putting a little time and money into a car, you'll probably find your options open up a little bit. Plus, you'll take a lot more pride in it when it's all said and done!
just my $0.02
Frank