It's not that uncommon, it's in what people look at as 'salary'. In Europe, salary is not just what you get (net pay), it's not even your gross salary (as it is on your pay slip), it also includes the taxes your company pays on your salary, too; plus any pension benefits, health care/SS contributions (including those paid by the employer), etc.
Once you count those, European 'salaries' come much closer to US equivalents (discounted for regional differences etc, of course). The 'US salary' is much more 'what it costs the employer' than the 'EU salary'.
I can't speak for Europe as a whole but in the UK a "salary" refers to the amount of money earned pre-tax by the employee (and not including any taxes paid by the employer). All job ads are written that way and salaries are discussed and negotiated in this way. Perhaps continental Europe is different in this regard, as you suggest, however.
Once you count those, European 'salaries' come much closer to US equivalents (discounted for regional differences etc, of course). The 'US salary' is much more 'what it costs the employer' than the 'EU salary'.