I've seen really bad 190 SL's go for way too much money recently even though the market is down. The cost of restoration is prohibitive but who knows.
It would be helpful to know the state of the car: rusted floors, fenders, trailing arms etc., engine running, and on and on.
I saw a totally useless car go for almost $30K.
The attached chart shows cars that have sold from "Fair" and below.
Go to the 190 SL Group, become a member, buy the club books, ask someone who owns one and then buy the car. Don't just jump in; there may not be water in the pool!