You are comparing outliners (big tech with huge salaries and outstanding benefits) with every employer in Western(?) Europe. How much does it cost to provide 6 weeks of vacation to everyone in the country? The senior engineer in Europe will have to support more people through taxes.

The market rates are lower because there is no market. FTA I only recognize one European company with somewhat global reach (booking.com). Europe doesn't have multiple companies trying risky businesses and competing for the top talent. European values (focus on equality, stability, WLB, etc) are in part responsible for this.