FTX supposedly had funding rounds that valued it at like $30B. This is equity, not deposits. Possibly massively overpriced due to crypto bubble, but likely that he could've extracted generational wealth from it.
I'd be shocked if they had any solid claim at even $1B using honest numbers. The crypto world loves to make valuations like “I just sold one to my buddy at $500, the other tokens are worth $45 trillion” but at the end of the day there just wasn't that much liquidity since most people aren't interested in the product. For a company like FTX which is getting fees from their customer's holdings that doesn't leave a lot of room for billions unless they could have cashed out at the peak of the bubble.
Or just settled for the generational wealth he'd get from his parents. You really had to try hard in this guy's position to not live a life of complete material ease, and he pulled it off!