Did my NZ to FAA no problem.
You can submit your Aussie CPL for a US Private, but that takes 2 months.
What I did was the 3 writtens and the 3 checkrides. (Private, Instrument Multi and Commercial Multi) all under Part 61. So if you have the requirements then you can do it in about 2 weeks with a couple of revision flights.
The problem is, most places wont give you a proper quote until they see you fly, (ie get you there and lock you in) or they have a very high flat price which is the same for the people that can do it in the minimum hours as those that take 50 hours.