I actually disagree with that. It all depends on your energy and how you carry yourself. Also, I've walked into M-B, Porsche and BMW dealerships looking how I look ("alternative" style I guess one can say, I don't even own a suit I don't think) and gotten just as serous attention as when I've walked into Ford dealerships. IMO it's the guy who can get people to treat them seriously without going the more pandering routes, i.e dressed-to-impress that really impresses me personally. I always thought it was cool and intriguing/curiosity inspiring to see someone who looks like they "don't care" (actually let's say more "artistic" in a non-trying-hard way) hop into an expensive Luxury Car, while you wouldn't do a double take to see a guy in a suit get into a BMW or Benz (i.e it's more expected), etc. Based on my own experiences, I feel this plays out with others viewpoints toward the same subject as well.
My Brother looks like a full blown Rock Star, one day he was borrowing an actual famous Rock Star's Porsche Panamera, and man you shoulda seen the looks of intrigued and seeming "impressed" attention he was getting.
Now, mind you, this isn't to criticize those who go the more professional and/or over-dress route, as again it's all about how you carry yourself. My Dad is Mr. Suit, has some of the nicest professional wardrobes I've seen and people regard him very highly even upon first impression, but he's a genuine and stand up guys, which IMO is what really counts.
.... I don't know how we got to this subject but I guess I felt like rambling as this is a subject that intrigues me.