We can get things cheaply here, but the importers have to order quantity to get the prices.
Years ago, I was contacted by a Taiwanese company offering RS-232 cards for the princely sum of about $1.50 each. The same card could be had in the shops for around $30. The caveat? I had to buy them by the container load, and a minimum order of 100,000. I could have sold them for $5 each and made a fortune, but didn't think I'd get the things sold - I couldn't see 100,000 people flocking to my door to buy serial port cards since computers of the day came with 2, usually a DB9 and a DB25.
We COULD get stuff cheap, but we have to buy in such bulk that it'd be wasted.
Then there's import duty. As someone's already pointed out, Ford and Holden need to be protected. Not because they're Aussie car makers - they're both American - but because they employ Aussie workers, and if production is cut to meet a lowering demand, those workers are now standing in Centrelink queues. Import duty makes the imported vehicle at least stand on parity with the competing vehicle offered by the company employing Australians.
Subsidies in the USA also make a difference. Those buggers get their fuel at reduced prices and I'm sure - because they definitely have a love of the automobile that MUST impact on decisions about manufacturing, importing etc - there's gotta be some assistance provided there too.
No matter what our dollar does, we'll always have disparity with the USA simply because of the other factors involved in motor vehicle production and the fundamental attitude towards motoring.
If Australia adopted the same attitude, we'd have 10-lane super highways, half-price fuel, and every city would have a car maker with an Indianapolis-style raceway nearby with parking for 50,000 cars so that people could attend the races on a weekly basis.