Hi Waitressvn,
You should be fine to ride, purchase and register a motorbike if you have an international licence.
As far as the cost of registration, I'm not exactly sure. The NSW Road Traffic Authority website (
http://www.rta.nsw.gov.au/registration/otherinformation/registrationfees.html) says it will be around $100.
Once again, I'm not too sure on the cost of insurance. Your best bet would be to call up some insurance companies and ask for a quote. Some to check are AAMI, Shannons etc.
But I would expect it would cost more to insure a 1000cc bike than a 250cc bike. It all depends on your age and location and what bike you have. Driving record, etc.
Also, do you want 3rd party insurance or comprehensive insurance?
Hope this helps