It's an interesting notion. It seems the well documented unrestored cars in pristine condition are the ones that often bring the high prices. At least that's my impression from watching what has been selling in the last year. The 5 speed transmission without a doubt will bring a premium, I'm no expert but I've seen estimates from some it should add 10-15% (not $10,000.00) to the price of an otherwise very nice car. I've also seen some very nice cars sell at surprisingly low prices or not sell at all.
I've been told by car dealers who seem to know the business that "on a given day with the right buyer and the right car you can sell a car at a very high price" but other times a car will sit for months on end before selling , or not sell at all until the price is dropped significantly. Then of course you have the economy as a factor in all this....?
But to me....here's my best guess I'll offer just for the sake of discussion... if a 230 SL were in flawless shape, mostly original, well documented with a 5 speed. $75,000.00+/- to the right buyer...that's my guess, Supposedly the Classic Center sold a car for 95K not all that long ago but I heard conflicting reports of what it actually sold for so who knows....Like the dealer told me, right car, right buyer, on the right day....