For 1985, according to this, the W123 200d was already out of production in Germany

The 200d Dieselmotor W124 limousine (sedan in the USA) was priced at DM 32,604 in October 1984

These were like Stuttgart taxicabs.

The last W123 200d limousine was sold in 1984. The price was DM 28,887.60

Them you would have to add to that, the option prices on the particular car you are looking at. They are here also.

http://www.meinbenz.de/preislisten/W123%20Preisliste984.htm

Isn't the internet and your Mercedesshop Diesel heads great?

I will leave it to someone else to find the answer to what the US= DM exchange rate was for 1984.

I do know of a brand new '84 500SEC lapis blue gray market car brought to California. The gray market importer paid the equivalent of $40,000 for it out of Germany directly.
(late edit:^^^ They cost about 88,464 DM new in Germany)

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1991 560 SEC AMG, 199k <---- 300 hp 10:1 ECE euro HV ...

1995 E 420, 170k "The Red Plum" (sold)

2015 BMW 535i xdrive awd Stage 1 DINAN, 6k, <----364 hp

1967 Mercury Cougar, 49k

2013 Jaguar XF, 20k <----340 hp Supercharged, All Wheel Drive (sold)