They are, in that order, Australia's top three export earners. You can find more details at the Global Higher Ed blog. I want to highlight here two things. The first is this estimate of the economic benefits of hosting foreign students:
Each international student (including their friend and family visitors) contributes an average of $28,921 in value added to the Australian economy and generates 0.29 in full-time equivalent (FTE) workers. Overall, this sees international students, and the associated visitation from friends and family contribute $12.6 billion in value-added.
The second is this table, with data for 2006 on the number of foreign students studying in different (groups of) countries:21.7 million) hosts five times as many students as the USA (306.2 million).