we did it packed a sea container with stuff that was 2500 across Australia and my car went by train that was 800, and we had the flights and 3 weeks accommodation at other end. IF i was you i would be prepared for having to stay longer in a caravan or holiday home as we ran out of time to find a rental it was harder than expected.
Yup moving is an expensive business Ahurani! Lol. MIL moved from Sydney to Mackay a couple of years ago. It cost probably around $3000, but she hired a small truck to move all her stuff and DF drove it up and back, so she really only had to pay for fuel for all the vehicles (they had a convoy..the truck, her car and another relative's car), accomodation for one night, and the truck hire.
I'd add on a bit more for car hire - I'd be inclined to double it to be honest. Car hire is always more than you expect, there are often 'hidden extras' plus you have fuel on top of the rental costs. We recently holidayed in QLD and VIC (a week in each) and our car cost us $700 for each week plus fuel and that was with one of the cheaper rental places.
Have you double checked the price to get your car sent via the train too? Your estimate seems a bit cheap. I had my car sent over from Melbourne to Perth 11 years ago and it cost me $900.
If you were to drive, you may need to increase your allowance for fuel too. You haven't specified what sort of car you have but I know our Mazda CX7 costs almost $80 to fill in Perth where the prices are quite competitive. I've been over the Nullarbor and back and fuel is not cheap at all.
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