Market valuation is based on perceived need over actual need. In my experience, European companies tend to think they need management types - middle managers, project leaders, etc - more than they need IT (of any flavour).

There are numerous reasons, but the most important one is that American tech firms are better-capitalized than European tech firms.

Europe has the individual talent, but their capital markets tend to be sclerotic and risk-averse, and in the case of certain countries, protectionist as well.

Because we accept working for less :).

Ultimately, if there are no other constraints interfering, the pay will gravitate towards being as low as workers are willing to accept (which ultimately is a function of costs of living).

In a way, every developer that feels "entitled to" high salary is contributing towards keeping the programmer salaries high, so it's in our all our interests to keep asking for more, not less :).