Dear Professor,
So that we can make some meaningful comparisons, perhaps you could add some detail to:
"He would be paying a lot more tax than you imagine. You fall prey to the trap most Australians fall into. The cost of living is higher in the US than you think and housing is more expensive than you imagine. There are more hidden taxes than Australia too."
We can work out Australian tax rates on income, we know what the GST is, we know we have to pay for medicare (as well as private health cover), but other than stamp duty, I cannot think of too many other Australian taxes (ignoring government charges for "user pays" things such as passports, pilot medicals etc).
So please let us know what these hidden taxes in the US are, and how the cost of living is higher than we might imagine. If you are prepared to educate us, we wont fall into the trap that you are alleging.