I would LOVE to have a properly-sorted W124 diesel - what an awesome combination of handling, fuel economy, and style!

Another thing you can put in your "box of fears" is that the engines in those cars CAN have problems with glow plugs that get stuck badly enough that one or more snap off when removal is attempted. It doesn't bite everybody, but it can be miserable when it happens.

Some owners recommend additional preventive maintenance to avoid this; you can read all about it on the Diesel Discussion if you buy the car.

I don't know what they're actually getting for them, but I see a lot of pretty stout asking prices for low-mile examples of that model.