I think this is a huge point that people really underestimate. I think a lot of people would like to go somewhere new and different for school (whether it's vet school, study abroad, whatever) -- and don't get me wrong, Australia is awesome! I love going home. I love my family, the food, the people, the towns, all of it! However, for an American moving all the way to Australia for school, you need to consider how much you're going to miss home.
Are you going to drive while you're there? Okay, well you'll need an Australian license after a certain amount of time and I hope you take a driving course because everything in the car and on the road is switched to the other side.
Will you work while you're in school? Goods and services are more expensive in Australia, but that's because people, on average, get paid more. Unfortunately, for a U.S. student on loans, you may not have the income to offset that. Maybe some more international students can chime in on that.
How often will you go home? When I go to Australia it takes no less than 36 hours and four plane flights. You can't just pop home for a weekend. Even going for a week is really too short when you consider the time spent traveling and the jet lag.
I only moved across the country for vet school. It takes me 5 hours to get home by plane, the currency is the same, driving is the same, and I understand the economy. That being said, moving across the country was too much. I almost count down the days until I can get back home and not have to travel back and forth across the country. I can't wait to get out and graduate and go back home. I miss my family and my horses every single day and while school is a welcome distraction, I never could have anticipated how much I'd miss home. I couldn't imagine moving to another country for 4+ years.