It might be a bit hard to believe, but in reality many passionate employees don't really care about the pay - they genuinely want to build a great product - but they are still paid well because the company looks after the top talent in every possible way.
He says he's giving all of his wealth away when he dies anyway. So I'm guessing he has plans to give it to causes he really thinks are important going forward. I'm pretty sure someone like Tim Cook doesn't need the cash so there must be a reason for the compensation and to be fair Apple's execution has been nothing short of incredible since he took over.