POINT OF ORDER
Doesn't [individual character] Charisma already factor into the merchant prices? I'm seeing claims that Tuco's system would ADD this functionality, but if it's already in the game...
It does, but it's not the main focus. You have to actually sacrifice stuff to the altar of favor, bartering, to get substantial discounts. As opposed to making it a key focus for the discounts which means that if you've done the bare minimum to get in to the grove, for example, you're on your way to that goal, and don't have to sacrifice anything to get it.
