AFAIK the S500 in US trim usualy has regular gas front shocks, IE about $100 each for Bilsteins.

http://catalog.eautopartscatalog.com/mercedesshop/sophio/quote.jsp?clientid=catalog.mercedesshop&cookieid=21B0XKG2A21B1EDBA8&baseurl=http://catalog.peachparts.com/&partner=mercedesshop&year=1992&product=L4000-40498&application=000353511

If you do not have ADS you are looking at $216 to do front shocks.

Which shocks are you talking about front or rear?

__________________
2006 CL500
2009 C300 4matic
1969 280SE
2023 Ram 1500
2007 Tiara 3200