On the surface, Nostromo's line is something of a lie: what he was afraid of losing was the silver, if Giorgio forbade him the island. But I hear an allegorical level, in which "hope of you" means hope in the utopian socialist future. I.e., to achieve that future the People must engage themselves to lawful society and continue their unlawful pilfering of wealth. If deprived of that, they would lose their "hope." Continuing on that level, Giselle's retort dismisses the need for wealth, replacing it with "soul."