For whatever reason the SC's dont seem to go very high in my experience - have a 42 in great shape - complete with distillate tank good rears, new fronts - paid $1200. Have a 50 SC in great shape incl new paint - runs good, good tires etc that I paid $1500 for back before market dropped.
I have seen good runners complete with decent tires but in need of paint go $700-800. I would have guessed $1000-1200 for a good runner compared to other tractors, but as I said, SC's seem to run low. For a non-runner I would probably not go more than $500-600 - maybe less if rough or in need of tires.
Check to see if motor frozen. Look for cracks, welds, repairs. Check tires and look for rust problems on rims
Good starting point for a rough non-runner would be scrap value in your area - assume about 4000 pounds. Personally I would try to keep it out of scrap heap unless its all cut up or sheetmetal with dead tires, rusted rims, cracked block, etc. But hard to justify on a non-runner.