I had no idea I was getting such an enormous discount. It explains a disconnect I had in a conversation with Tuco, though. I couldn't figure out why he kept saying the price of certain potions were higher and how I wouldn't have enough money in act 3; all the while I was in act 3 with more money than I could reasonably spend.
It just happened that I was playing a warlock with the astral tadpole talent. I guess it makes a huge difference in pricing. More than I would have anticipated, by far.