1) How personally validating a job is to a person

2) How valuable the job is to society at large.

To see how those might decouple, consider Superman continuously turning a crank to provide limitless energy for society (credit: SMBC [0]). Fabulously valuable to society, extremely lacking in personal validation for superman.

In general, you'd expect salary to correlate with 2, and inversely correlate with 1, since the sense of validation is in effect part of the compensation you're getting from a job. It also seems pretty common to (IMO wrongly) think that 1 and 2 are tightly coupled: the jobs that produce the greatest societal value are the ones that feel the most personally validating. But that's just because modern society is far more complicated than our brains were evolved to handle. Identifying the actual value of a job requires following a complex chain of incentives and value production through the vast networks of businesses and organizations that comprise our world.

Sadly for those instincts, it is probably true that a programmer writing a piece of code that makes $business_process_c56_2 0.1% more efficient, which is then run billions upon billions of times is actually producing more value in net than a teacher who changes the lives of O(1000) kids over their lifetime.

[0]: https://www.smbc-comics.com/index.php?db=comics&id=2305