In reply to Sunny77's question I have done a few quick calculations using tax calculators from the ATO web site and the Hong Kong IRD web site. The results are quite interesting.
US$8000 per month is $96,000 per year. This is around HK$750,000. If you live in Hong Kong you will be taxed HK$119,200 ($99,200 if married).
After tax you will take home around US$81,000.
If you earn the same salary (US$96,000= A$122,000) in Australia you will be taxed nearly A$45,000. Take home pay will be A$77,000, or roughly US$61,000, compared to $81,000 in Hong Kong. To take home US$81,000 in Australia your pre-tax salary needs to be A$171,700!
To answer the question, you can live quite nicely on US$8000 per month in Hong Kong, as long as you don't have children at international schools and so long as you don't expect to have the same standard of housing as you have in Australia.