Why are the pearl buyers excited to buy a pearl at the lowest price even if thwley do not stand to profit directly from the sale? What does this reveal about human nature?

All the pearl buyers are in collusion. They work for one man. We can speculate that the buyer who gets the lowest price might get some type of extra financial reward. The pearl buyers regularly take advantage of Kino and his people. Although the villagers know they are being cheated, they accept this is the way of things. The pearl buyers also accept that cheating people is part of their job. They have developed a repertoire of various lies that they give the villagers to convince them that their pearl is not worth much. The pearl buyers seem to take pride in this. Greed and justification of greed are at the heart of human nature.