They are awesome cars. But not as run down as that. I would pay $300 for it. Just a little over scrap value because its unique.
I know how you feel. Before I owned an e30 I dreamed so hard about owning one that I would even consider restoring a model in similar condition to this 190e. But once you learn to have patience and realize that the 80s are not really that old, eventually you can find a much better example for a couple thousand.
Just because its beat and rare and probably could be obtained for a few hundred bucks does not make it a good deal. Be patient, do some searching and be ready and willing to travel. Then you will find the car you want and not have to dump several thousand into a car valued at only a few thousand. 80s cars are still new enough that buying an already decent example is better than going full restoration on a junk yard wad of steel, even if that wad of steel was free.