I have just been trying to clarify this as well.
Good to hear you didn't get slugged on the boards.

I got some masts sent from NZ recently. The sender stuffed up and the declared value was over $1000. Got charged not only GST, but roughly the same amount again in Customs Duty charges. (They charged to to charge me the GST basically

- not happy!

)
Since I want to arder a new ski from the USA, I spent a fair bit of time today on the phone to Customs and then Fedex.
The current situation is (as far as I understand it) that anything that is below $1000 and
"Posted" to you from an overseas seller that is not a collector of GST (so not from Amazon or some other online stores that collect GST for the Australian Govt.) does not attract GST or duty. If it comes by sea or air 'freight', the situation seems to be: Under $1000: GST is levied but not duty. If it is over $1000, both GST and Duty/Customs are charged.
So my question was, what does 'posted' mean? I finally found an answer on the Fedex website:
Note: "Importations by post" is not restricted to goods carried by Australia Post. The ATO has ruled that goods weighing less than 31.5 kgs that are transported to Australia and delivered door-to-door by an international express courier service or similar door-to-door courier are goods posted to Australia.
So it looks like my new Ski from the USA (under $1000) sent via Fedex, should arrive GST free. Phew!

I guess I will only be buying 'used' windsurfing boards from overseas with a declared value of under A$1000 from now on.