The gold in Robot of Sherwood represents a raw kind of greed. Even though it is required to power the spaceship and not for its monetary value the selfish procurement of it delivers the same consequences. The gold is the only thing the robots care about. It is a means to an end and the path to get there is of no concern to them. People are only valuable in terms of their labor and once they are used up they are discarded. Its not that different from the feudal system of Robins time that exploited the serfs to work a lords fields. Its also a lot like our corporate system today where people are called resources and used with little regard for their intrinsic worth as a living being. The robots are so focused on obtaining the gold they dont consider what might happen when they try to fly the ship. They can only see one tiny part of the problem and their inability to view the whole picture is their downfall.