Talking about average salary....in Europe can be extremely misleading. Europe consists of 44-ish countries, with VERY different levels of cost of living, and - no surprise - VERY different levels of salary. So the second you publish average numbers, they next set of questions arise - difference within Europe?....
Undoubtedly the rising number of remote workers in Europe, (with lets say French Salary living in Greece for ex.) will, slowly level the field a bit, but not drastically.
Even the extremes of North America will vary drastically.