Students of Ravenwood should be able to make potions or elixirs. Maybe instead of buying extremely expensive elixirs with crowns, you should be able to learn to make your own. Also, you could refill your potion flasks standing right where you are instesd of having to visit the minigme kiosk. Maybe you have to be a certain level to make certain potions.
Sorry it's not much, so if you have any ideas, please post. Happy adventuring