Though Nostromo is obsessed with growing "rich," it remains true that every character uses the San Tomé silver merely as a means to an end. In this case Nostromo's real goal is independence -- security from betrayal. Note that his denunciations of the rich now include the poor; the effect is to widen the scope of possible betrayers to all mankind, and clarify the allegory in which the People, having rejected their exploitation, will not rest until the entire world is free from the prospect of it.