I get people like that too. Ive gotten good by how they talk, and questions they ask, statements made, (all over the phone) that I'm 95% right, and they get quoted higher than anyone else. Because I know theyre going to be a pita to deal with throughout the whole transaction, Ill make sure I get paid for the pita factor. Example, part would take 2 week, and cost 1k normally. They get quoted 4 weeks, and 1200-1300. Theyre never going to be happy anyway!
So in answer to OP, yes hate it. As biz, Im nice as can be. As individual, not so much.
Oh, also Ive found, these people are almost 100% of the time, NEVER going to buy anyway. I seriously think its some kind of bizarre hobby, really.