The most common components to fail are the fluid reservoir units. Every tech or other knowledgeable person I have ever talked to all say the struts very seldom ever need to be replaced. The cost of the reservoirs should be comparable or less than the basic shock price you listed of $160 each. I had mine replaced on the '93 500SEL and they were around $125 each plus labor.
One would have been easy to change but the other one is behind part of the exhaust system run, and not as easy to reach on your back. Just in case you were considering doing this yourself if this is found to be your problem.
Anyway, just be darn sure your struts are truly "bad", so I would get another opinion. And, yes, there is a huge difference between the struts and shocks as Sixto says. The price reflects that difference, but worth it IMHO.
