I was listening to The Michael Shermer Show where he was interviewing Marian Tupy and Gale Pooley on their new book Superabundance.

A statement made by one of the authors hit me. We buy things with money, but we pay for them with time. They went on to discuss how economics made a mistake by measuring prices in terms of monetary cost instead of measuring the cost of goods/services in work-hours.

One of the dramatic examples is how much in terms of time we have to pay for an hour of light.

From the Washington Post article. And with modern LEDs, the efficiency is even better.