FWIW, I just spotted a 240D on eBay, a 1982 model supposedly with only 8700 miles on the speedometer. Buy it now for $22,500
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=6329&item=2441725531
It will be interesting to see if this one ever breaks the reserve!

Dieseldiehard
1971 220 (gas) 4-spd manual 104041
1979 300TD w/ ’85 turbo engine 289560
1983 300D 237490
1985 300TD 206150