To follow on from Sinnertwin, the total estimated cost with BBTS assuming that shipping quote is accurate would be ~A$1,850 including GST. That's something like $800 more than the cost I estimated with buying it direct and going with the MyUS route!
I'm not always happy with how MyUS packs items when we consolidate but in cases where you don't consolidate (you wouldn't consolidate anything with Unicron) they just use the original shipping box and ship it as is. My wife has ordered many high end Disney collectibles this way and never had anything lost or damaged. You can also insure the shipment from MyUS to Australia for US$2 per US$100 of item value (ie US$12 for Unicron's US$575 value) for peace of mind.
In the end it's totally up to you but you will certainly be paying a lot extra.