In Act 3 of "The Crucible," What does greed have to do with the witch hunt?

The  main connection between greed and the witch hunt comes in the person of Thomas Putnam.

We find out that many of the people who have been accused of witchcraft are people (like George Jacobs) with whom he has financial disputes.  We find out that he has put his daughter up to accusing Jacobs.  We also find out that if a person is convicted of witchcraft, their property gets auctioned.  As Giles Cory says, only Putnam has the kind of money needed to buy many of the properties of the people accused.