I think most of the OP thread applies to about any car, MB or otherwise. Unless the vehicle is collector status, then you will not recoup your money. I went through this with my '81 240D, a '96 Ford Contour and a '98 Dodge Neon. Don't mention both '98 Jeep Cherokees.
Some will say the MB parts cost a lot. I found some cheaper than the other vehicles. Some more expensive. Other like brakes about the same.
I would say, that the 240D ran OK when I bought it. It could not do over 55 mph. Mainly due to the throttle bushings be gone. A lot of the cost was that it ran so long with out any real maintenance from what I could see. The radiator hoses didn't look much better than the pictures in a Chilton's manual.
I would agree that with used vehicles say 10 years or older, you need a second car. I bought a '15 Volt a month age. I could get a new intermediate shaft for my '00 Ford Contour SVT. You can get them for an Auto, but not a manual. So to say its just MB older cars is not correct.