Had the pearl buyers system been changed before?

Yes, the pearl buyer's system had been changed before.

"Before you were born, Kino," he said, "the old ones thought of a way to get more money for their pearls. They thought it would be better if they had an agent who took all the pearls to the capital and sold them there and kept only his share of the profit."
Kino nodded his head. "I know," he said. "It was a good thought."
"And so they got such a man," said Juan Tomas, "and they pooled the pearls, and they started him off. And he was never heard of again and the pearls were lost. Then they got another man, and they started him off, and he was never heard of again. And so they gave the whole thing up and went back to the old way."