I sold my "driver" 1982 308 GTSi in 2000 for $26K. It had 88K miles on it, a rebuilt motor, Tubi exhaust, Titanium shift gate and shift knob, and a Ferrari 348 steering wheel. That was good money then for the car. I'd suspect a pristine, low-mileage, carbureted 308 GTS might be in the low-to-mid $30K range...
Bob
Bob