This is true, and still true to some extent once you compensate you can't compare the two numbers. There are large costs associated with living in the US like health insurance that just don't exist in the UK where I live.
Paying a given salary in Germany is a lot more expensive for a company than paying the exact same salary in America. There are both more taxes on the employer side and more labor regulations that cost money to comply with. The number of hours worked tends to be different, too.