It is a nice car, but I would not go over 2500.

Assuming the mileage is correct (and the odometer was not broken for several years), there is probably a lot of deferred maintenance that needs to be done, or will need to be done in the near future.

I would look for:

Condition of wiring harness. Has it been replaced? If not, that will need to be done.

Does the blower motor work? Is it original? This is another time consuning and expensive repair.

Condition of the bushings in the rear suspension. They are typically "done" by 150k and this car reportedly has 160k. I would want to replace them due to age if original.

Has the AW70 tail shaft bushing been replaced?

Condition of the front end. Check ball joints and tie-rod ends for play. Check for presence of power steering fluid in the boots on the steering rack. I've had to replace the PS rack in a few 240s between 150k and 175k. Check for play in the wheel bearings.

If all of that checked out, I would have no problem offering 2500 cash. For each issue, deduct cost of parts from 2500.

4k is way too much. It is nice, but it is still a 32 year old car.