At some point you also have good old fashioned blackmail. Once the mark has been tricked into giving away a small sum, you can now hold it over their head as b

At some point you also have good old fashioned blackmail. Once the mark has been tricked into giving away a small sum, you can now hold it over their head as blackmail to give you a larger sum - they are as fired/going-to-jail after giving away $X as for $10X, so with the stick of telling their bosses what they've done and the carrot of "maybe I can get you out of this if you give me a little more", the con artist can keep coming back to the same victim over and over.