Duty and GST is payable on all goods purchased of value over AUD 1000.00 (or thereabouts - wont go into it now)
Duty is not payable, only if the goods are duty free due to a free trade agreement with the overseas country (US, Thailand, NZ etc) or if there is a tariff concession, or if the goods are under an FOB value of AUD 1000.00
Not sure whether you're importing will be duty free unless there's a tariff concession available.
Make sure you stipulate to the supplier that the shipment terms must be DDU (essentially means door to door duty unpaid) If they are shipping to you on CFR/CPT or CIF shipment terms or they say "yes we've paid the freight to Sydney/Melbourne etc" be suspicious because this may leave you paying import terminal fees etc.
Your total Duty, GST and Customs Entry Fee will probably come to about AUD 350.00 - depending on whether you're shipping Seafreight, Airfreight and how the Customs Broker calculates it.
The most important thing is making sure the shipment is "door to door" or "DDU"- otherwise you could be up for something like:
AUD 310.00-380.00 + GST for import terminal fees and Customs Clearance
AUD 350.00 for Duty/GST/Customs Entry Fee
Also, the "$1000 rule" isn't only what you bring in on a plane. Your cargo will be duty, GST and Customs Entry free if it's under an FOB value of AUD 1000.00 - whether you've brought it in your luggage or bought off EBAY etc.
Hope this helps.