The demographic of BMW owners tends to modify their cars more than the MB set. They also seem to go for the more performance "image" that BMW pedals. As such, most of the people who would tweak on a benz end up in BMW's to begin with. With that interest there has sprung up a large aftermarket. There are enough top notch BMW tuners that there is some level of competition among them. For most people who would modify a benz price is not as much of an issue. If it is, they tend to go to BMW where they can get it for less. (though the longterm performance, durability, and resale are open to discussion)

Just my opinion...Lee