Cliff,
These figures are supposed to represent actual sales data so the differences could be in what specific cars have actually sold for. IMHO a '63 to '67 230SL is probably "worth" about the same on paper except for some minor improvements as time went on. As far as the 185 in '67 thing it really doesn't add to the value as perhaps a 1 of 185 '67 Corvette with a 427 would. In other words there was nothing dramatically different in a '67 Pagoda vs a '66 or '65. Also keep in mind that the "model year" of the car started in the previous September so many cars built at the end of 1966 were sold as a 1967 model (including mine for instance). The VIN number of the car along with a table on the Technical Manual tab will tell you the month it was produced.
As far as realistic value, I look first at potential rust, then overall mechanics, then body panels, then interior. To me, if all of these sincerely check out then you should be good to go. I know if I wanted to sell my car, I would not accept $30k for it in this market if that tells you anything about the car you are looking at. As always, pictures (Exterior, interior, engine bay, undercarriage) are with a thousand words as they say. Feel free to post some here...I GUARANTEE you'll receive some replies!!
Kevin
(I see that I posted at about the same time as Jordan and it seems that we concur!)