Many European cities aren't exactly low cost of living, and those that are have even lower salaries.
In the end someone who was working at Google in the Bay Area for 15-20 years can retire if they didn't have life style creep (which is different than cost of living). Not the case in Europe.
'Someone who worked at one of the best paying companies in the world can retire after 15-20 years'.
This has nothing to do with Europe. This is particular a tech thing
It's a particular tech thing in not Europe, specifically.
Europe has tech companies. They just pay less.