I think there is another factor missing from both equations. If someone is willing to be available for overtime, that is valuable in and of itself, even if that

I think there is another factor missing from both equations. If someone is willing to be available for overtime, that is valuable in and of itself, even if that person is never asked to do overtime. The company has the option of asking for overtime with employee x, and not with employee y, and could be persuaded by employee x to pay for that optionality.