This type of wholesale Benz bashing is not of much benefit to the OP. $125 per hour to work on an old Benz? WHERE? Independent mechanics usually run around $55 to $80 per hour, which is right on par with any other make. Parts are readily available for any vintage model.Mercedes supports their vintage cars better than any other make. Parts cost are right on the mark with other makes as well. The “labor-intensive” remark is also way off base. Vintage Mercedes’ are very straight forward cars to work on. Have you ever worked on sub-compact Asian cars or full sized domestic vans?
I would agree that that according to the OP’s description that the SL is probably in the $4000 to $6500 range depending on your local market.