what is the cheapest way to fly from atlanta to brisbane?

I just spent a semester abroad in Prague and met two of the most amazing people ever. Unfortunately, one lives in Brisbane, AU and the other lives in Dunedin, NZ. Small problem, indeed. I've heard about around the world flights being good for people who aren't worn down easily and that they can be cheaper, but I wanted to see if anyone out there would know. Please!