+1. Although it is possible that insurance costs were becoming a burden. Let's flip the question: why are they continuing with a scaled-down cast and crew? Answer: this isn't a sitcom where a cast change can change the whole character. The shows reruns do well, they have strong merchandising, and it would cost to buy out Jamie and Adam ' contracts so there's still money to be made if you can scale down the enterprise. And frankly I think even Kari, Tory and Grant benefit if the Mythbusters franchise continues...their roles on the show live on in the minds of the public and they have enough celebrity to last a while.