The term expresses an exceptionally good performance by someone
The term is used in such a way that if the person (who the term is being directed to) actually is getting paid for whatever s/he is doing, then merely saying the term (and technically expressing the obvious) actually means to express that that person is going above and beyond the job requirements and should be getting paid a lot (maybe more than s/he is getting paid).
If money is not already involved then it just expresses that the person is doing such a good job that it's like s/he is getting paid and still going above and beyond the requirements.
(Childris works as a cashier in a grocery store making an hourly wage of 7.50$)
Childris: Hey, did you see me yesterday? I scanned through 227 items and had all of them bagged within 5 minutes
Fellow Cashier: Hell yeah I did, you were getting paid!
Person 1: I've been training to play basketball all summer, so I challeneged my younger brother 1 on 1 and he beat me 15 to 2
Person 2: Wow, your brother is gettin' paid!