Decoud is playing on the old phrase, "Unlucky at cards, lucky in love."
But Nostromo's romance with Paquita is, as we have seen, a metaphor for the People's
romance with their rulers.
The deeper meaning of Decoud's "propitiation" is that Nostromo might
be underpaid and exploited, but he is successful and needed vis a vis the rulers.
Nostromo (apparently speaking at random) then retorts that he accepted the mission
without complaint: i.e., he is not trying to have his reputation and eat it too.