Bilsteins are the cheapest quality strut/shock you can get. There are cheaper ones but I wouldn't trust them on such an important part of the car.
The will be far cheaper than OEM replacements.
Also, no offense but what Jason said is true. You bought one of the most expensive cars to maintain, don't expect anything to be cheap.
Last edited by SamDoe1; 08-15-2012 at 10:30 AM.