SPOILERS

If I remember right, everyone is in on the act in the restaurant except for the rich guy who for a moment thought he had killed the lady. It is implied that after their failure to trick him out of his money, they are going to kill him and dispose of the evidence. However, in the final scene we see that they are running the same elaborate fraud in the restaurant as last time, but now with the rich man acting as a waiter.

Therefore, we can conclude that the rich man saved his life by agreeing to sign up to the fraud scheme and join their team.