The top end of engineers and researchers in artificial intelligence earn magnificent salaries. That domain is not, itself, the top end of software engineering,

The top end of engineers and researchers in artificial intelligence earn magnificent salaries. That domain is not, itself, the top end of software engineering, it's a specialization of it with its own salary track. You aren't actually comparing like for like here, because most engineers doing work in "artificial intelligence" aren't even pulling down the salary you noted for the top end of plumbing (which is itself wildly unrealistic).