If I made bio fuel, and labor was not a factor....probably $1.50 a gallon.

Of course there is setup costs, but you can setup a processor using a water heater, or rob parts from one and make your own using 55 gallon drums. I have all the stuff to make one (less hose, fittings and valves) and have $80 invested in two new barrels with removable tops, everything else was free.