In practice, this usually gets me because I'm rather impatient for it... but I understand that reducing the heat and simmering longer is a decent way to concentrate more ingredients into a potion of the same size. If you're concerned about expense, it's not the most cost-effective way to make a potion, but... there's value in a reputation for efficacy.

[No one wants watered-down potions; it's just sense.]

If you're interested in growing your own ingredients, I'm sure Myr would have some suggestions for getting started. A green thumb comes with the antlers, for fauns.