I’ve never seen European salaries quoted post tax. In which countries is this true?
In Germany the company share of social insurance is another ~20% on top of the employees pre-tax salary.
It is not nearly enough to explain the wage disparity between SF/US and European salaries.
What most people are interested in is how much of their pay is take-home pay. In the US, the take-home fraction of your pay will typically be somewhat higher. It's certainly not the case that software engineers in the US are getting bigger notional salaries but then paying a larger fraction in paycheck deductions than their European counterparts.
By tax, I mean income tax. I've only ever seen "salario bruto" in my contracts, in job adverts etc.