We've got one colleague who likes to calculate those things. They changed overtime rules a bit. When they asked him to do some work early in the morning for reaching the targets, he refused. When the boss asked for details he sent an excel sheet with all the overtime company and tax rules in it. It turns out you only earn $5 net for coming in at work at o-dark-hundred.

Of course that sheet spread rapidly and management is now very surprised they can't find anybody to come in early.