Sure, and while I'm not the official authority on in-game prices, I would set the price of a potion that would fully heal a character Gothax's level at 150 col and one that heals about half at 75 I guess. If you are going to do that, though, I'd rather you edit your current post so that he buys them from Ryuusa's shop but you could make it so he's just buying more if you want.