I have been in contact with Leroy's Big Valley Gunworks leroygun@nemontel.net in Montana USA and they can export to Australia using DHL, Danzas and a few others, for a single rifle it would break down to

cost of rifle
Leroys fee $75US (may have gone up)
Air Freight $250US
customs brokerage $75US
GST
minor airport charges

So to import a single rifle has gone up about approx $250US

I know Australia Post uses DHL, Danzas at times to move mail so they are full of shit!