But Luffy is the nicest guy ever...
Try asking him to share his meat
Anyway, my point was that it shouldn't be only about money, or riches in general, but to be able to 'twist' the plot of a quest to get an ending fitting *my* purpose, and not that of the quest giver.
Let's say that someone hires you to free a manor from an usurper and the one who hired you comes along. I'd like to betray the npc who hired me and let him fight alone the 'last boss' and then kill them both and take the manor for myself