I've been watching StockX, Kogan, Dick Smith, Catch, etc. for the past few weeks and this seems to be the lowest anyone's currently offering and hovering around the lowest overall (so far).
Goods with a customs value of A$1,000 or less are subject to 10% GST at the point of sale. For goods with a value over A$1000, an Import Declaration will need to be filled out, and import duties, taxes and government charges will need to be paid at the border.
64GB - currently in stock
256GB - currently in stock
512GB - ordered on request
1TB (modded) - currently in stock
It's not clear which model is used as the base for the 1TB modded version, presumably the 64GB one. It's also not clear what SSD they use as a replacement, but they sell / advertise alongside the other Steam Deck units the WD SN740, and there's not many 2230 NVME SSDs in 1TB capacity, so a good guess that it's probably that. If you can source a 1TB 2230 NVME SSD from somewhere it's probably cheaper to buy the 64GB version and the SSD and replace it yourself, but if you're not confident to do that or lazy, buying the pre-modded version would be your option.
According to the listing, it may also come with a power adapter. "Please note that many of our devices are import versions and may not come with a local charger. In those cases, a plug adapter will be included in the box."
After reading a lot of so-so feedback on Expansys (particularly around customer service), I was questioning whether to pull the trigger on the 64GB over the weekend as the stock said "ordered on request". This changed to "10+ in stock" this morning, so I took a punt on it. I received the shipping tracking link this evening, and according to Toll tracking, it's already been handed over to Toll in Hong Kong and has been sorted to destination. Your mileage may vary (as may mine given I haven't received it yet).
Shipping was $22 for me, for a total of $732. At that price I figure, for the 64GB model, $399 USD + 10% GST = about $640, add Australia tax to round it to a more likely retail price of $699, and the difference is enough to pull the trigger on it rather than the faff of VPN, US prepaid credit card +fees, reshipper, etc etc etc. or waiting for it to launch locally (whenever that may be).
Also I hope they don't repackage it and then pass on this headache to the next person.