He does this year after year. He controls the company with his private class of shares, so he sells his public shares as more of his options vest. It's how he has so much real money that he can do with as he wants. The shares he sells, get replaced with options that vest. Been going on for years and the always increasing stock buyback keep options in the money year after year. A great gig if you can get it, but long-term its always good for shareholders too.