How many miles did your 240 have on it when you bought it? My theory is that between 125K and 175K alot of the things you mentioned need to be replaced.
I bought a really nice '85 300D that only had 125K on it three years ago. I've had to replace all the things you mentioned and a few more. I have also owned a '84 300SD and have a '90 300SE. Both had over 215K on them at time of purchase. They have been very trouble free. But all the stuff you mentioned had been replaced prior to my purchase.
That's why I'm so concerned about this purchase. If and when a car broke, my tech was here in town. Breaking in a distant city could be a hassle and expensive.
At this point I simply can't afford to put out alot for a car. So I know I'll have to take my chances. I do agree that Mercedes prior to the "luxo rice burners"seemed to e better.
I don't think they had the worry of price competition prior to 1990. I remember that a Lexus LS 400 was about $10K less than an E Class that had a six banger, and a V8 was $20K more.
91 300E 120K
90 300SE 275K (sold)
92 BMW 525iM 120K
90 BMW 525iA 175K
85 300D 175K (sold)
84 300SD 245K (sold)