From my own questions, usually asked through google text2translate, i have discovered quite a few girls are bought here to pay off debts at home in China . Haven't worked out as yet how they go from debt to being sent to Australia and who controls them once there here. But you can be sure they have to pay off the airfares etc and of the 180/hr they probably don't pay off much of their debt.
The last girl said she was off to another city after about month, and many girls get moved around Perth from house to house.
The Chinese girls appear to be part of a very large organised syndicate or syndicates.
So if you're paying for sex with a Chinese girl who doesn't speak any English, please treat them with the utmost respect. You'd be horrified if it was your daughter.