Take the time to read the harmonized tariff schedule....
At first it seems like a 20,000 page nightmare but if you spend some time with it you will be able to zoom in, zoom in, zoom in. Once you are in the category for Motors you can start to investigate the different percentages. You will be quickly outraged when you see obvious corruption:
"All 1hp electric motors" 4%
"1.02hp electric motor 12" in diameter painted blue" 2%
"0.99hp electric motor 3lbs for use grinding meat" 1%
This is the result of assholes sneaking things into the books... but sometimes you can beat them at their own game.
In the US hub motors fall under one of these - something to the tune of:
"750W motor" 4%
"750W motor to be used as the sole source of propulsion for an electric vehicle" 0%
So on my last couple of orders I have customized my deliver to be outfitted with larger phase wires, better connectors, etc in order to reasonably rate my motor at 750W and I import them duty free. 750W is just about right too... that is about 1hp and that is about what it takes to make for a reasonable low power ride.
Do your homework boys
(though in AU you are going to get screwed either way)
A good broker should find this for you - but he can only go by what you tell him.