Unfortunately, the best deal on these is probably from the dealer.

The aftermarket struts don't have the springs - the ones that MB sells have the springs already on them for a little bit more. Everybody says that springs don't wear out easily, but that seems not to be true. I used to have a Volvo 960 - I replaced the struts but didn't replace the springs. The ride only marginally improved. I wished I had replaced the springs (only $30 each) as the technician had recommended. The car only had 65K on it, so I didn't think it needed the springs. It turns out that age is as big of a factor as miles. Remember, springs are holding up the weight of the vehicle when it is standing still as well.

HTH