@farmerman,
That's the problem both with jewel heists and art theft. How do you turn a profit on it? But, of course, at a certain level there exists a network of both professional thieves and fences who'll pay ten cents on the dollar value of a perfect diamond or on a Rembrandt painting. And when the value is in the millions, ten cents on the dollar is a lot of money for the thieves.
But, I agree with you: a lot of these so-called robberies are staged for the insurance money. But read the story at the link I posted. The reporter says there's a vey professional gang, known as the Pink Panthers, operating in Europe and elsewhere right now. Some fascinating bits in that story.