Overview
You can do this once you acquired the Cauldron and the Revival Pill receipe.Revival Pils cost 1000 Bei.Heal Powder and Magic Powder both cost 100 Bei each.One of each nets you one Revival Pill which sells for 500 Bei and hence nets you 300 Bei profit. You can buy 99 of each item while at the trader per time, but I think you have no limit on how much you can carry. Click on +, until you hit 99 of each and click buy, do this over and over without leaving the trader menu until you run out of money (Make sure you have similar ratios of each times to speed things up. To speed up purchasing and during crafting, hold down left mouse button on the + tabs. Doing this can make the game somewhat less painful as your NPC’s usually spams loads of items, but it won’t matter if you have say 9999 of it.