dieseldude, unfortunately I have paid a higher price for HD's when I have purchased them, so either I was ripped off, or there is a cost difference for the various types of Bilstein shocks. That may or may not have anything to do with the type installed on the cars out of the factory, it was only an opinion of why most MB's headed to the USA don't have HD's or some other model shock installed.
The basic point I was trying to make was that HD's do make a difference, and are very good options for certain Mercedes models, and certain styles of driving. Your information from the old hand tech added another good reason to use them; that being if you live in a rural area or drive through rough road conditions routinely.
I would also argue that "the factory" has many components, and I doubt one design or production decision rests with one person or is made solely with performance factors in mind. If performance factors do drive those decisions, more power to them!
Besides, if "the factory" got it right all the time, this website would not get the traffic it does since many of these topics would never come up.