What do these presumably highly-paid C++ developers work with exactly? And what is their background? How much do they make in London? I have a degree in mathem

What do these presumably highly-paid C++ developers work with exactly? And what is their background? How much do they make in London? I have a degree in mathematics, am ~36 years old, but only worked as a web dev. I'm thinking about taking courses in mathematical statistics or physics. I want to "get out" of web dev. This type of job would be a huge step up for me. Just unsure how to begin a career change...