How costly is it to replace one rear strut?

Replacing struts is like replacing your shoes, its best done as a pair. The genuine Mercedes strut is nearly $400 each (look at www.rockauto.com to check aftermarket prices). My labor guide says about 4 hours labor to replace both.

One side replacement is ok , Air spring cost around $550 labor $ 250 sometimes need to becalibrated for proper hieght .