Did you rent this tool? If not, I cannot afford $600 to buy a tool for a one time use. Four hours do not sound too bad if you have to spend that kind of money. I know Performance Products
http://www.************************ has the same tool listed for $457 and it is also available for rent but, I do not know for how much. I do not think MercedesShop has a tool rental program YET (hint). If you bought it, may be you can rent the tool to members of MercedesShop and get some of your money back...