I would add two reasons in addition to those already discussed: 1) Some of the difference is structural. Upper middle class gets a larger share of the wealth i

I would add two reasons in addition to those already discussed: 1) Some of the difference is structural. Upper middle class gets a larger share of the wealth in the US than in most European countries. An American professional in any field is paid more relative to the median income than in Europe. 2) International comparisons are often misleading. This is true even if you adjust the numbers for purchasing power and structural differences (such as benefits/taxes paid on top of the nominal salary). For middle class and above, the marginal cost of employment is higher in the US than in Europe, because you are expected to contribute more towards healthcare / education / childcare / retirement / unemployment / parental leave / etc from your personal income. An American employer has to pay a larger fraction of those costs directly to their employees, while an European employer can rely more on other taxpayers. The second point sets American middle class salaries higher relative to GDP per capita than in Europe, while the first point sets upper middle class salaries higher relative to middle class salaries. In a truly open market, tech salaries would converge globally, but there are currently far too many legal and cultural obstacles for that.