Loans have to be repaid and I'm not talking about liquidity. If you have a billion $ in cash and use it to fund a billion $ research vessel, you have a billion $ research vessel. You're still a billionaire. Gaben owns large portion of Valve, a multi billion $ company. The only way for him to no longer be a billionaire is to either

• Sell his stake in Valve and burn, give away or otherwise loose all the money.
• Devalue Valve to the point that it's no longer worth billions of $.