Most of that money is likely in Valve stocks. Ie. let's say Valve is worth 10 billion, GabeN owns half of Valve so there's 5 Bn right there.
I realise that, but that's still a much bigger value than I would have expected from Valve. Wow!
Bet Shiken that COD would outsell Battlefield in 2018. http://gamrconnect.vgchartz.com/post.php?id=8749702