> How much do healing potions and stuff like that cost, and how does the money work in Paradise?

Uhm, unless Chuks has different ideas, I would just try and match it up to what it should cost in most RPGs. So like... Look up DDO, and see if you can find how much the potions in that game are and model it after that. 

Money is like... coins that you get from defeating monsters. You get small amounts from monsters and larger amounts for taking on quests and such. 

If that makes sense...