This is a bit misleading taken at face value as the US has loads of smaller cities with far lower cost of living whereas almost all of Australia's software jobs are in Sydney, Melbourne and smaller capitals. The Silicon Valley wages are at least twice as good as Sydney and nowhere near a proportional cost of living increase.
https://www.numbeo.com/cost-of-living/compare_cities.jsp?cou...
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.
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.
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.
Silicon Valley pays USD$500k to staff engineers. CTOs for relatively large companies in Australia don't make that kind of money.
The UK value translates to just above £29k as an average annual salary. That might just about be an average annual new graduate starting salary across the whole of the UK, but even there it seems low. In terms of all software engineers it is most definitely off by several grand.
$71k is just barely above what the BLS reports as the 10th percentile for software developers in the US[1]
[1] https://www.bls.gov/ooh/computer-and-information-technology/...