Around how much would this trip cost?

It depends on when you want to fly and where you want to end up in Australia. A good site for pricing trips is Kayak: a href="http://www.kayak.com/" rel="nofollow"http://www.kayak.com//a which will search across multiple airline booking sites to find the best fares for your travel dates. For the dates I looked at in September, the airfare is $1500 and up. The cheapest airfares for dates in November and December are about $100 more