There are some for sale, go to cars.com or autotrader.com and search for the entire US, about 30 cars show up. They aren't worth much, most are the in $10-12k range, one's with 50k miles or so are in the $16-17k range. Race cars $20-25k. Guess it depends also on how well they've been taken care of.
If someone wants to buy mine, I'll sell it for $18,500. Two-owner car, and it's fully sorted out, 137k miles. 6-spd manual coupe. Don't have good historical receipts, but the following has been done and documented:
New clutch
New clutch slave and master cylinders
New Clutch hose
Timing Belt and water pump replaced 1 month ago
Front engine re-sealed - no leaks!
Recent brake bleed/flush with Motul 600
New oil cooler seals
Koni shocks/struts and coil overs all around
New brake pads - Pagids in front and Hawks in rear
New PORSCHE rotors all around
Sparco seats
Low temp thermofan switch
New dme relay
New fuel filter, plugs
Trans fluid recently changed
SS brake lines
New battery
New windshield
Freshly painted in January.
AC blows ice cold, all electrics work, including roof and rear hatch.