A gallon of gasoline contains about 28,6000 Calories of energy.
A gallon of whole milk contains about 2,400 Calories of energy.
A gallon of milk has enough energy to power an average person for an entire day.
A gallon of gasoline has enough energy to move an average person, some friends, and a two-ton vehicle somewhere from ten to sixty miles.
Both gasoline and milk cost about $3 per gallon. Both are extremely undervalued.
If I had been born a few thousand years ago, I would have had almost no leisure time, and I would have needed to work all day long just to keep myself fed and alive... trying to find the 2,000 or so Calories needed to keep myself from heading into starvation.
Back in the present, if I take the value of my salary and benefits package for last year, and divide it by 365 days, I am earning about $200 per day.
In the past, or in the present, a gallon of milk, with it's 2,400 Calories, could sustain me for a day. A gallon of milk to me, back then, would have been worth a day's work, or about $200.
By the same token, if I happened to be a slave back then, and worked all day, for TWO WEEKS, I would do the same amount of work as can be done with one gallon of gas. (See
Real Gas Price)
Two weeks of work would have been worth at least $2,400.
In reality, a gallon of gasoline is really worth somewhere around $2,400.00 per gallon.