Hi Liz,
We have a Bmw X5 and here the value has plummeted, but over in Oz they have held their value quite well, so my car would be valued at $40000 and the taxes i was quoted was $8750, the way they work it is all dependant on the value of your car, is it deemed a luxury vehicle etc, the following text is from the document that Karmann Shipping sent me you should be able to work out the costs from that i think

it really is quite confusing, i really want to take my car but the process is really daunting and to be honest the only bit i am sure of is you need to get a personal import form from DoTaRs before you start anything.......Hope this was some help if you have anymore questions dont hesitate to ask i will try my best.....
Regards
Paul
Australian Import Taxes on most cars are 10% Duty (5% for ‘off road’ 4wd vehicles) and 10% Gst. Duty is paid on the customs value and Gst is paid on the total of the customs value + duty + cost of shipment. Usually the Customs Value is based on the Australian ‘as landed’ value which can be as low as half of the actual Australian market value. In only very few cases, if a vehicle was purchased before March 1998, then the CV is based on the UK purchase price less a depreciation allowance.
Valuation method advice can be obtained from Australian Customs and the destination clearance agent can recommend a local valuer for an ‘as landed’ valuation estimate. An initial guide to the full Australian market value is available at www.redbook.com.au.
Items packed inside a car travel free of charge. A list of goods is required by customs and quarantine and these would be cleared separately from the vehicle.
A guide to the costs would be £1,500-£1,700 shipping, £100-£300 shipment protection, A$2,250-A$2,750 in Australia excluding taxes, annual registration and insurance