I don't like vendors who think they can take advantage of me for a few extra bucks because of what they see (isn't that a form of prejudice?)
Same with haggles at flea markets or garage sales. If you don't label your prices I'm immediately not interested. I'm a demographic that looks "put together" and thus "wealthy" when in reality I'm basically broke and would file for bankruptcy if it'd clear my debt.
So when I come across a haggler (usually an old guy or a foreigner from a country that has a culture of haggling) I tend to avoid them because I don't enjoy that process. Thats why America came up with price tags and fixed pricing for stuff. Way less hassle. Only idiots really savor the process of haggling. It sucks.