Taking the idea of monthly income and using some creative accounting lead me to this number as my submission.

Way back when the original Cities: Skylines came out (actually shortly before) I decided to experiment with building a dam, not realizing that the game modeled water flow to genuinely unexpected results. Cue laughter.

This would trigger rarely when a staff member goes on break and there is no break room in the museum. And yes, I know it is called a staff room in game, but the joke wouldn't work then :p