SOPS these are some of the reasons.
Market size 10x AUS, so far more sales to pay for the showroom etc.
No Luxury car tax (33% above $60Kish in AUS)
No 5% import car tariff.
Much shorter boat ride from the factory.
Average sales tax in USA 5.75% rather than the 10% GST.
All adds up to cheaper cars, food, living etc.