Real estate prices in Sydney and Melbourne are in the million(s), but incomes are ~100+k AUD. Some people earn 200k+ as a principal engineer, but that's pretty much it.
In America you have much more cities where you can find a decent job and different lifestyle. If New York is too expensive, you can move to Raleigh, NC. I don't think that exists in Australia.
There is also a very low degree of innovation in Australia, it's all related to real estate and mining.
Personally I just feel like it's not worth building a life here unless you get a large inheritance, but for an immigrant, America is a much better place to build a future.