The events of this story suggest a negative view toward wealth in this period. In particular, there is a negative view of the accumulation of wealth and of greed, more generally.
We see this clearly through the fate of both Tom and his wife. Once Tom makes a deal and receives the money from the Devil, note how different he becomes. He has a successful moneylending business but he becomes a vain and ostentatious man who nearly "starves" his horses. His character, therefore, suffers as a result of his great wealth. In addition, Tom also becomes "crack-brained," meaning that he is no longer rational and sensible.
The fact that Tom is taken away by the Devil at the end of the story is how Washington demonstrates his disdain for greed. This idea is reinforced by the fate of Tom's wife, who is never seen again after trying to strike a bargain with the Devil. That neither Tom nor his wife enjoy a long life shows that a desire for wealth was not favored in this period.
It is also worth noting that Washington creates a link between the Devil and vast sums of money. It is from him, for example, that Tom receives the pirate's fortune. By creating this link, Washington suggests that wealth is associated with evil.