Jamie Hyneman and Adam Savage have a reported net worth of about $8 million. Grant and Tory have reported net worths of $2 million. And Kari is about $1.5 million.

Not bad, but both Jamie and Adam were well respected visual effects artists, builders, and model makers before Mythbusters. Mythbusters primarily shot at Jamie's shop.

Grant and Tory both worked at ILM. Kari was an employee of M5, Jamie's company, when she was put on the show.

So, not terribly rich, but about what you would expect. $1 - $2 million "net worth" is more attainable than you might think. As net worth includes assets and what not. They have enough money to take substantial risks that might not pay off.