I ran the numbers based on the Clearer Thinking exercise and found a rate at which I’d trade money for time that I was comfortable with (in economics, this is called the marginal rate of substitution). It’s based on the amount of money you earn for each hour you work, after taxes, and for me it’s about US $50/hr.
However, the rule of thumb is only theoretically grounded if you are paid by the hour. I’m salaried, so I am not expected to work a particular number of hours per week, and I can’t earn $50 more for each additional hour I work. I’m still willing to apply this number in my daily life because it “feels right”.