On another SE site, I wrote in a comment
What's in it for X?
(X is a person.) I was asked what this phrase meant. I looked in three online dictionaries of idioms and couldn't find it. It showed up in the urban dictionary as an acronym but I would think a more formal dictionary should have it buried somewhere.
To me, this phrase was a less blunt way of saying
What would X gain from doing your grunt work for you?
I'm looking for a documented definition and usage notes.
(I don't think it's necessary to wade through the question on the other site in order to understand and answer this question.)