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.

There is a very linear relationship between time and money for the one who pays the employees though.

Nobody says “you know boss, that two hour meeting today was a total waste of time, please deduct two hours worth of my salary from my paycheck”. So the company quite literally pays for everyone’s time who was at the meeting. And that is a function of who is present and how long the meeting goes. It is very much not a function of productivity/value.

And the point of having a, more often rethorical than real, taximeter showing the cost of the meeting puts this into perspective. The more people you invite the more the meeting costs. The longer it goes the more it costs. The goal is not to abolish all meetings, but to make people think if the bang to buck ratio of the meeting is right. To instill a culture where people prepare for meetings, they have concrete questions or decision outcomes they are looking for, and to criticaly think about the length of the meeting and right-size the invite list.