What important fact do we learn about the the pearl buyers' business methods in The Pearl?
An important fact that we learn about the pearl buyers' business methods is that they are part of a system whose goal is to make the largest amount of money for "the only one pearl buyer with many hands". There is a monopoly in the business of buying pearls in La Paz; the different buyers in the village are all controlled by one large entity. The buyers who have contact with the public receive set wages and do "not profit beyond their salaries", but they do get "disciplined" if they do not bargain effectively in the interest of the "one pearl buyer". The whole system is rigged against the common people, who have a vague awareness that they are being cheated, but no experience by which to know for sure, and no power with which to do anything about it.
When Kino approaches one of the pearl buyers, he is told his pearl is worthless and offered a ridiculous price for it. The buyer calls in two other buyers to back up his assertion of the pearl's lack of value, and points to their corroboration of his estimate as proof that he is not lying. The villagers, however, do not know that all the pearl buyers are controlled by the same "one pearl buyer". All have been coached in the same methods of cheating the customer.
Although Kino and the village of La Paz are fictional, the business methods described are an accurate portrayal of methods used to keep simple people in subjugation throughout history. By taking advantage of the villagers' isolation and naivete and preventing them from bettering their situation, stronger powers grow richer while the people remain struggling in poverty.
When Kino insists that his pearl is worth more than he is being offered and refuses to sell it to the pearl buyer, the pearl buyer knows that he "had played too hard" and will be in trouble for not having been able to fool the simple man and make a deal. Desperate to avoid the censure of his bosses, he offers more than he had originally stated, proving that his first offer, which he had portrayed as being generous, had been completely out of line (Chapter 4).