Actually if you look at the brand demographics Lexus owners are older and have higher incomes, that doesn't neccisarily mean they're more affluent though as I don't know if they count wealth as income. I don't see the same difference here that you see there and I've been to several Benz dealers, one of them is a combo Benz/Rolls/Maybach dealer and they're very stuck up and unpleasant, when my dad was looking to replace his LS they soured him on a Mercedes completely (a 62 year old man who makes almost $500,000 a year) by how nasty they were, one salesman about knocked him down to beat him through the door then let the door shut in his face. Maybe you have to be really rich to expect that kind of abuse, who knows. Another dealer I've visited in a less affluent area is very nice, but I couldn't get him back to another Benz dealer after that.
Other than that one dealer which is obviously an oultlier the dealership experience seems very similar to me.