Professional employees (lawyers, accountants, scientists) make less in government (usually much less), but non-professional employees usually make more in government.
How are you defining "professional" in this context?
There's a classical sense of professional it seems you're reaching for, but I'm having a hard time thinking of a non-professional white-collar worker which would do better in federal government than the private sector.
Eg, surveyors are clearly professionals. Software developers? IT?
Software engineers, IT, EE, ME, tend to be paid significantly less than they would make outside of gov service. This of course varies a bit by level, but it's generally true.
This comment has been downvoted but I wanted to highlight that it is quite correct, people actually working in the public sector tend to be paid poorly compared to similar private sector jobs, this is a bit of a new trend where the previous generation in the US was more familiar with public sector jobs being good paying reliable jobs that could help secure a family into the middle income bracket but that time has passed.
I am excluding, by the way, private contractors working in the public sector which tend to be grossly over paid but lack any sort of pension benefits.
Professional employees (lawyers, accountants, scientists) make less in government (usually much less), but non-professional employees usually make more in government.