No, it assumes some linear relationship between pay and time. Which is a little iffy for salaried workers, but only a little.

My employer gets about 40 hours/week of "work" from me, whatever that might consist of. I cost them $X every two weeks in pay and benefits. It's pretty reasonable to say my attendance in a one-hour meeting has a $X/80 cost to my employer.

You don't need to overcomplicate this. The employment relationship is pretty simple at its foundation: the employer buys the time of its employees.