I would guess hundreds of millions, if not way more. I'm sure his salary was reported as being $30m base + $25m stock per year back in 2011.

I said bizarrely because in these situations the media & general public seem to always think that people like this can't survive without work. The guy is undoubtedly incredibly passionate about design and almost certainly a workaholic. The grandparent is talking about him going on design the future of automobiles - maybe, maybe not. It felt like I was suggesting something against the grain, which was why I prefaced it with "bizarrely".