There is no logical reason to be mad about the 1-gil undercutters. Doesn't change the fact that many people, myself included, hate 1-gil undercutters and will not buy from them. It's a psychological thing, not a logical thing, but it is a thing. Undercutting by massive amounts is of course just stupid, but there is a middle ground of reasonably lowering your price by small increments without being that guy that shoves his 1 gil in your face as if to say "yeah you like that, I beat you by one gil, what you gonna do about it?" Obviously they are probably not thinking that, but hot damn you feel like they are!