Green’s Dictionary of Slang

bottom line n.

[Yid. di untershte shure, the bottom line, in the context of denoting the final profit/loss figure on an account]

1. the end result, the final assessment.

[US]D. Woodrell Muscle for the Wing 186: The bottom line is, all these punks have got to go.
[US]Source Oct. 224: Bottom line, however, nobody smacked sawed-offs to our collective mugs.
[US]Source Aug. 32: Bottom line is, you gotta live this shit to be this shit.
[US]A. Steinberg Running the Books 17: Bottom line [...] this cocksucker didn’t stab you in the throat, right?

2. something steady, reliable.

[Aus]L. Davies Candy 104: Candy was the steady income, the bottom line, and I was on special projects.