FitzTech and Cefiro...
The import duty is worked out at 15% of the purchase price of the vehicle NOT including shipping. There are further costs incurred with clearing customs (around $150 at last check) but then GST is worked out on the total: Vehicle purchase price, shipping and the import duty (in other words you are paying a tax on a tax - GTS on import duty... I await the comments on that one!). The easiest way to work out your budget (in my humble but experienced opinion) is to convert the purchase price from yen to AUD (I work it out at around 2 yen below the published rate to allow for fluctuations and bank fees), add 15% to this, add around $2,000 for shipping and customs and quaranteen clearance fees, then add 10% of this total to this total. Also, if you didn't already know, only a RAW can actually apply for an import approval so ensure you have one before the vehicle lands at an Australian port or you will have to re-export or destroy it. Then there are the obligatory compliance costs etc as I assume you already know.
DJ984, different importers have their own policies and I cannot speak for any other than myself but I can assume that most would either pay the taxes etc as they arise with your money (how I started), or just pay them themselves and pass the cost on to you. The only other taxes that most importers / consultants wouldn't cover would be the state government stamp duty which is payable upon first registration or on transfer of ownership. These vary from state to state and currently in SA consist of 4% of either the market value or total cost of the vehicle; whichever is the highest (of course).