For US citizens the visa procurement should happen AFTER you have secured the tickets. It is a relatively trivial process and generally simple approval, unless you're a convicted felon or otherwise wouldn't qualify. If you head over to the Australia/NZ/S.Pac. forum here you'll see a sticky thread that will help you get the ETA visa for free in a "pay it forward" sort of way. I recommend going that route if you aren't otherwise entitled to a freebie.