How is wealth defined in The Pearl?

In The Pearl, wealth is virtually synonymous with power. Those with money are invariably the ones who exercise power, both social and political. This helps to explain why the doctor is so determined that Kino will never get a fair price for his pearl.
Kino is a member of the indigenous population. Not only is he dirt poor, he also occupies the bottom rung of society's ladder. He will never get to live in any of those nice houses he sees when he goes with Juana to the doctor to get help for Coyotito. And that's just the way the doctor wants it. He doesn't believe that indigenous folk like Kino and his family are entitled to the best things in life. If Kino should receive a fair price for his valuable find, then he'll be able to move up the social ladder, potentially occupying a higher rung than the doctor himself. For a member of the dominant race like the doctor, this would be too much of an insult to bear. So he does everything he can to put Kino back in his box.