I am trying to figure out the original price, but l can not seem to find it, I am gonna sell one and is planning to find out how much l should sell it for after what l know about the car. please help

l think they went for about 10 000 -13 000 thousand

In 1973, the 450SL was ABOUT $11,000.
l recently saw one at a show with the original window sticker that listed it as $11,800 or something near that.. Do not base your price on the original one because the car is value has probably raised dramatically depending on the condition and mileage.

Look here: http://nadaguides.com/default.aspx?LI=1-22-1-5013-0-0-0&l=1&w=22&p=1&f=5014&y=1973&m=1115&d=4200&c=13&vi=76601&da=-1

You are aware that is a world-wide site? The prices varied depending on in which country the vehicle was purchased, as well as the options on the vehicle.

Also, the original selling price is irrelevant for a 35+ year old vehicle. The value of a dollar is 1973 is not the same as a dollar in 2009. What matters today for a vehicle of this vintage is the car is condition and how valuable it is as a collector is item.

according to NADA:

Original MSRP: $13,340.00
Current value: between $10,850 and $23,800 depending on its current condition.