50 billion assets are properties of investors.
Here are what he could have made,
1) From management fees
5billion * 2% * 15% = 15,000,000 - cost
2) From profits
5billion * 15% * 15% * 20% = 22,500,000 - cost
Plus 50% taxes, and other expenses and losses, it's quite possible that he only has 14,000,000 net worth.