It's been a long time since there's been a good Australia sale. Fares tend to hover at $1,000 off season, and slightly higher during the Australian summer, from the west coast.

You might look at Qantas's vacation site. They advertise package deals with air and hotel included. They have an $1,899 package on there right now that includes Sydney, Melbourne, and Cairns, with hotels, for 12 nights. Having said that, you won't get 100% mileage on Qantas, so if that's a factor you might might to book with United.
Qantas vacations site

I find Australia the best place to "burn" miles. Should you have miles, that might be the thing to do.

Have you looked at the UA promo where you get a free international ticket in coach for two round trip tickets from SFO to JFK? There are some restrictions (the JFK ticket cannot include a Saturday night stay, must travel before early April), but that might be a good workaround if you can plan well in advance, and assuming UA has availaibility for award travel after you secure the ticket from the promo. Look at the UA board and UA web site for more details.