Well the way Potions currently are is "Restore X% of HP (Max X Amount)". That's fine for food items which are always in high demand, but for potions, that needs to change. I propose level-scaled potions.

Potion: Level 1-15: "Restore 50%(60%) of HP" Level 15-30: "Restore 20%(25%) of HP" Level 30-45: "Restore 10%(12%) of HP" Level 45-50: "Restore 5%(6%) of HP"
Hi-Potion: Level 15-30: "Restore 50%(60%) of HP" Level 30-45: "Restore 20%(25%) of HP" Level 45-50: "Restore 10%(12%) of HP". Requires Level 15
Mega-Potion: Level 30-45: "Restore 50%(60%) of HP" Level 45-50: "Restore 20%(25%) of HP" Requires Level 30
X-Potion: Level 45-50: "Restore 50%(60%) of HP" Requires Level 45

That way, the cooldown timers would be more justified, I think. Obviously, this wouldn't be flawless, and it should scale level-by-level, but you get the idea, right?