From the pictures worst case scenario I would pay 3500 if it was running and does have the Buick V6. I think it goes up from there depending on a lot what these fine folks have said, that I will echo for myself:
1. Rust rot anywhere. Surface rust I can deal with but rot in these areas doesn't help the price:
----frame (look near spring mounts)
----windshield (hard to tell until you fold it down and check near the grommets)
----tub (check the lips with the sheet metal is curved and folded...flat areas is simple to repair but these areas are not)
----behind diamond plate (as was mentioned)
2. How does the dash look? modded out with extra holes, aftermarket switches, and wires? A good dash with working gauges and wiring counts for a lot to me.
3. I'm not a fan of the SoA and the reverse shackles if I am looking for an older CJ. I want something as close to stock as possible. I think most people on the forums would agree with me (maybe not) that putting the springs back under at least would scare less potential buyers away?
4. I notice it has a roll bar up front installed. That could be points if it is done well. I'd also be wary of how its installed and if there is rust where its bolted to or through the floor. Having the tops and doors is a plus for sure especially if they are in decent shape.
5. If everything works as it should (obviously running, but shifts fine, lights/hazards/accessories) then more points.
If all those points were met and from what I see in the pictures...if I was buying another CJ *I* would pay 5400-5800. And I think you could get close to 7k down where I am at...
Anyways, good luck! If you don't own a CJ already I say KEEP IT!!!!