What exactly is the relationship between Perception and Rarity?

The appraisals say, "Increases item rarity by Perception x1." I'm wondering what this actually means. My Perception is over 600 so it obviously isn't x1 and even getting gear to increase my perception my appraisals are not rising and are instead capping out at a base of 115(no buffs) which is the same thing I was getting over 60 perception ago.

Is there some sort of cap I am unaware of?

This is a bit depressing as I'm wasting my time getting this gear from red scrips only for it to do nothing except waste my time.