Seems like a great price on the 105 4iii power meter.
Only available in the 170 mm crank arm length.
Next cheapest I can find (and cheapest for other sizes) is probably direct from 4iii website in the US as they recently lowered their retail prices to 299 USD. Once you include shipping this works out to around 480 AUD (plus tax, probably).
Can be had for another $20 cheaper at Chain Reaction Cycles (sister site) using CLEAR2020 - https://www.ozbargain.com.au/node/549516#comment-8953041