Here's a suggestion I have: For more powerful potions (Like haste, negative energy, etc.), could we have separate bottles to be sold for like 25-50gp? Just to make them challenging enough that people probably wouldn't want to risk making them unless they were -very- proficient in the skill.
The reason I say this is becuase my character currently has like a 75% chance of failure on some of those uber ones, but he more or less doesn't worry about failure becuase, well, he loses out on a whopping 5 gold each attempt.
We should keep the standard 5gp bottles for most recipes, though. Making it too pricey would scare away everyone who isn't over level 10. I just suggest making the higher-level potions higher in price. I mean, think about the end result: If I can 100% brew those neg energy potions, that's about 20 potions I can make for 100 gold that normally cost 750 gold EACH as scrolls from NPC shops... 100 gp from 20 vs. 750 PER bottle... Yeah, you get the idea.