Without digging too far, seems hit net worth is around $6 billion. Obviously that’s nothing compared to say Bezos but if he wanted to ride a dick-shaped rocket into space I’m sure he could arrange it. He does, however, own the sub that holds the records for deepest crewed dives in all 5 oceans: en.wikipedia.org/wiki/DSV_Limiting_Factor
As you said though, he seems to be pretty much chill and until the day he passes away I think Valve is safe. And that will be a sad day…