What dates are you looking into? I just put in 12/22 to 12/29 (Houston to Sydney) at SideStep.com and the lowest price was $1935 via American Airlines.
It really doesn't matter, but I had put in a wed. to a wed, thinking that would obtain better results. I think I put in Jan. 8th-14th.
You can try flying as a courier, that's where a company checks in documents into your luggage and you get a discounted plane ticket. I flew a few times to Asia in the 90's as a grad student on a courier fare and the ticket was less than half the price of a commercial ticket. The drawbacks are that you can't check in any luggage and can only bring in a carry on. Of course this was before 9/11 so I don't know if they changed the regulations on that.
United Airlines Flight 377 320 More Information Houston Intercont (IAH) San Francisco (SFO) 07:25am - 10Dec, Wed 09:48am - 10Dec, Wed Nonstop Coach 4hr 23min Connecting flight wait time 12 hours 50 minutes United Airlines Flight 863 744 More Information San Francisco (SFO) Sydney (SYD) 10:38pm - 10Dec, Wed 08:05am - 12Dec, Fri Nonstop Coach 14hr 27min Flight Duration : 18hr 50min Layover Time : 12hr 50min Total Trip Time: 31hr 40min United Airlines Flight 870 744 More Information Sydney (SYD) San Francisco (SFO) 04:15pm - 26Dec, Fri 10:43am - 26Dec, Fri Nonstop Coach 13hr 28min Connecting flight wait time 4 hours 0 minutes United Airlines Flight 318 733 More Information San Francisco (SFO) Denver (DEN) 02:43pm - 26Dec, Fri 06:13pm - 26Dec, Fri Nonstop Coach 2hr 30min United Airlines Flight 716 320 More Information Denver (DEN) Houston Intercont (IAH) 07:20pm - 26Dec, Fri 10:39pm - 26Dec, Fri Nonstop Coach 2hr 19min Flight Duration : 18hr 17min Layover Time : 5hr 7min Total Trip Time: 23hr 24min Its $19655.55 after taxes and fees. link