I would question the sources for your price values.
The definitive sources for values on cars like this are Hemmings or better yet, CPI, or Cars of Particular Interest.
I have a CPI book from 2000 when my subscription ran out. Even then, a 1985 500SEL had an "Excellent" value or $9750. This car would not qualify as "excellent". This is CPI's description for "excellent":
"Nearly perfect condition. The vehicle has been professionally restored to the current high standards, but a few exceptionally well cared for original cars may qualify. All components are original or exact replacement. Most "excellent" cars are not driven more than a few miles per year, if at all. There are vehicles, usually due to an interesting history or special circumstances, which will sell for more than CPI's "excellent" figure, but these are extremely rare and would require extensive documentation. Some buyers are willing to pay more than the current market value for a specific vehicle. CPI cannot determine how much of a premium over market value an individual is willing to pay. Conversely, some sellers need to sell their cars immediately and may take less tha the prevailing market value."
The CPI scale translates to a 1-5 scale as "Excellent" being a 2 and "Good" being a 3.
This car would fit the "Good" condition in CPI. In 2000, that was $7350
Here are some data points from completed (sold) eBay listings:
with 123k on it - $4200
1985 Euro version
, much more desirable than a US spec model - $4550
with 92,000 miles - sold for $6100
that's a little rough, but only has 63k miles: $3256
This is the sort of research you need to do, which took me all of 5-10 minutes. And these are actual sales - not advertisements with outrageous asking prices which mean nothing, because there is no indication if those cars ever sold, and if so, for how much.
Look at this data, I think my numbers were pretty realistic.
I'm not being critical, but based on the factual data out there, your asking price is unrealistic. You can try to sell the car for that amount, but it's not going to sell, at least not in our lifetime.
As a comparison, and someone mentioned this as a data point earlier, look at the sales on 560SELs from the same time period. A much more desirable car, and the values reflect it. If this was a 560SEL it might command $10k.
The only real value in the 500SELs came in the Euro versions, as they had the nice bumpers if the car wasn't Federalized and much higher horsepower output due to the lack of smog hardware and adjustments.
Again, I think you need a dose of reality or you need to convince whomever came up with this price that the car is going to be in the garage for a long, long time if this is the price point they're looking for. The market data simply doesn't support it.