You are talking about my hardest battels:
It is allways the same: A guy comes in with suite and tie, everyone serves him as his favorite customer, he will be seated, served coffe, everything will be done for him. If he comes in with shorts and t-shirt, they ask him, if he had just opend the wrong door (exaggerated!).
Some salespeople cannot be tought to treat everyone like a potential good customer. But of course, it is a matter of experience. If You learn from Your first 100 customers, that a well dressed customer is a buyer and the casual or sloppy dressed ones are just askers, then, if You are a little bit lazy, You will concentrate Your efforts on the "good" ones and not on the "lousy" ones.
Only very few salespersons can really accept a sloppy customer as a good one. And here in Vienna, we have had lots of Russians, who come dressed even worse than Americans

on holiday. We should know, whats going on. But some never learn.