Apart for the importation problem/cost.
You also have the 'road legal' problem .. the vehicle must meet Australian Design Rules (ADRs) in order for it to be 'registered' for road use .. unless you have it 'wrecked' for parts (broken down and sold in parts). (Or it is very old .. umm 25 years IIRC)
For a motorcycle .. the minimum costs appear to be above $2,000 ... think a car will be around the same. Speedo in km/h, brakes, emissions, crash protection, headlights dip to the left ... etc etc...
An alternative ...? Don't pay for the shipping to OZ, leave it in the last place .. and sell it there? Then buy something in OZ if you want. The kiwis had a more liberal scheme ... so that might be an alternative? Bring it to OZ on the carnet .. them ship it to NZ and pay import charges there and sell there ... Any kiwi comments?