With half of Luna houses empty, there is no competition and so you have inflated prices. 1/4 of the houses sell potions. Also having Luna as a hang out, means more people shoppers in Luna. Personally for me, I make more money with how things are since I have a Luna vendor. With what I hear with the SA expansion, I am eager to see if the new Gargoyle city becomes the new Luna. I am sure having 2 places to shop may bring down the price some. But I guess we shall see.