I know alot of people like to bash on Amazon but really the answer to the OP's question lies with the manufacturer ECOVACS. You can view their Australian retailers on this webpage:
https://www.ecovacs.com/au/where-to-buy
That particular model the 920 is not sold at any of the other Australian retailers (apart from ebay which once again would be the ECOVACS own store), and the Amazon shop is ECOVACS own shop, which their own webpage links to.