In Act III, Giles Corey brings in a deposition against Thomas Putnam. In that depostion, he claims that Putnam has had his own daughter falsely accuse another man (a man named George Jacobs) of being a witch.
According to Corey, Putnam wants Jacobs's land. He knows that if Jacobs hangs for being a witch, his land will get auctioned off. Corey says that Putnam is the only person around who has enough money to buy such a big plot so he will get it for cheap.
So Corey is saying Putnam is using the witch trials for his own economic benefit.