Aside from that, and this isn't Australia specific, but the acceptance of WFH over the last year across industries is quite exciting, with regards to reducing CoL.
They are saying that Silicon Valley salaries are much higher than Sydney, and the cost of living in SV isn't anywhere near double (as you point out, it's probably cheaper than Sydney).
Info
Consumer Prices in San Francisco, CA are 7.55% higher than in Sydney (without rent)
Consumer Prices Including Rent in San Francisco, CA are 39.86% higher than in Sydney
Rent Prices in San Francisco, CA are 91.12% higher than in Sydney
Restaurant Prices in San Francisco, CA are 22.48% higher than in Sydney
Groceries Prices in San Francisco, CA are 18.67% higher than in Sydney
https://www.numbeo.com/cost-of-living/compare_cities.jsp?cou...
You are correct and other cities can be checked if anyone cares to do so.
https://www.numbeo.com/cost-of-living/compare_cities.jsp?cou...
She regularly looks at house prices in Sydney and dreams of selling our house and moving to Sydney but frankly I would never move there. I would visit, but I would not move there.