And by self contained, I mean a field of supercrop that is used to power its own conversion into fuel, and transportation of itself to its point of consumption, and to keep all the people involved in that process at alive (at a minimum) and happy (for example, powering their computers so that they can join in these discussions).

You can discount the people costs, but if you do so then they'll die, which tends to have a deleterious effect on the efficiency of the system.