The Question and Answer section for The Pearl is a great resource to ask questions, find answers, and discuss the novel.
One would be not overstepping one's place in society. Kino was breaking this rule when he demanded a fair price from the pearl merchants for his pearl. He further broke this rule by attempting to travel to the city to sell it himself.
Kino and Juana represent the poverty of the villagers. The pearl offers them a way to get ahead.... to lead a better life. Unfortunately, social oppression and colonialism aren't going to allow Kino the chance to change his situation. Everyone...
One cost to Kino and Juana was the life of their son. The opportunity of attaining wealth cost the couple the life of their most priceless possession.