I do this kind of math all the time, most recently to decide how to get home from the airport ("Is an hour of my time worth more than the corresponding ~$60 delta?" Turns out it wasn't, but this only led to depressing thoughts about how an hour of my time now is worth vastly less than it was in my first year of law school, even if not directly to me in the latter case, for dramatic purposes -- ie, deliberately not an apples-apples comparison -- but still). Morale is low and sinking around here.