You're absolutely right. You don't want to get a car like this for fix-up and resale in normal circumstances. By the time you get it fixed up nicely, it will be high-mileage with little resale value to the general public. Most people are terrified of anything with much over 100,000 miles, and completely afraid of 200K+. This is what happily keeps the price of those diesels affordable.
Seems like the best bargain is to buy one for yourself and keep it until its a "parts" car. I'm actually trying to calculate how long mine might last, and worrying about where the NEXT diesel is going to come from. The creampuffs with reasonable mileage and evidence of good maintenance are getting harder to find. I feel like I'm in one of those post-apocalypse Mel Gibson movies (Mad Max) where I'm trying to keep the ancient diesel technology running as long as possible.
I have to admit the interior condition of a used car is a big factor for me, even though everything can be fixed up. Just seeing a nasty interior makes me feel the driver was careless.
Just for interest, take a look at this car:
http://cgi.ebay.com/ebaymotors/aw-cgi/eBayISAPI.dll?ViewItem&item=595288712
I'm gonna watch this one just to see what the market will pay for it.
Ken
'82 300D