I have no idea if the disparity is as much now but at one time, postal employees were far better paid than other federal employees.
In 1974 I was a lowly GS-7 working overtime one Saturday in the federal building. Around 11, I took my lunch break and was eating in the break room. A young man who was a janitor came by and was cleaning up. We got into a conversation and he was a postal grade 1. We compared salaries and he was making more than I was.
My job required a college degree along with scoring pretty high on the FSEE. I think his required nothing other than being able to work.
The level 1s and 2s have been reserved for disabled veterans for most of a century. Expressing jealousy over the payment to multiply injured and disabled war veterans is not polite.
The big differential was at GS 5. Before Postal Reorganization postal PFS 5 was tied to GS 5 ~ your typical postal worker at that level was a clerk or a carrier. After Reorganization the postal workers got something like a 10% to 15% pay raise in the first collective bargaining agreement. It was very much in line with the then very high rate of inflation brought to you by JIMMY KKKATAH.
GS5's and so forth in the US government did not get a pay raise that year, nor the next, that was comparable to the Postal raise.
That SAVED TAXPAYERS TENS OF BILLIONS OF DOLLARS.
Again, postal workers are paid out of postage revenues. Government workers are paid out of tax revenues.
Every now and then you'll hear some uninformed regular government unionista complaining about the disparity where Postal workers get paid more ~ to which all I can say is of course, they work for a living.