I just wrote a long post explaining it, and somehow I wasn't logged in, it got posted as AC, and now it's not here anymore. I am very frustrated because I spent about 20 minutes doing calculations.
Here's the gist of what I had put:
The 10-to-1 figure is for energy, not volume.
A barrel of crude is 42 gallons and has 1.7 MWh of energy. Current market price is $105 per barrel. That's 40.5 kWh/gal. Corn oil has 94 kWh/gal. (Calculated from 120 kcal/tbsp.)
That would mean you could make 1.8 gal of corn oil from a barrel of crude, and corn oil should cost $56.66/gal, but you're saying you can get it for $4, I assume in bulk. So what's the problem? Consider how corn oil is produced: You extract the oil from the germ of the kernel. The remainder of the corn is not useful for oil. That's the part your missing. Here's the calculations on that:
According to wikipedia, a bushel of corn yiels 1.55 lbs of corn oil. Corn oil has a density of 77lbs/gal. So in other words you need 50 bushels of corn to make one gallon of corn oil! A bushel is 8 dry gallons. Raw corn has 132 kcal/cup. That means that 50 bushels of corn has 844,800 kcal of energy, or 982.5 kWh.
So there's your answer: it takes 982.5 kWh of corn to make 94 kWh of corn OIL. A factor of 10.5. Pretty close to the 10-to-1 figure. Divide our $56.66 cost by 10.5, and you get a much more reasonable $5.40/gal. Figure in some government agriculture subsidies and oil subsidies, some market economics between the two goods, sales of corn byproduct (they don't just discard the portions not used for oil) and you have something very close to your supermarket price on vegetable oil. The 10-to-1 number is just an estimate, but it's a pretty darn good one.
Adjust your tin foil hat. :)