What makes you think that nobody can get the billion?
Insurance policies require you to pay a certain amount guaranteed, then pay back a much larger amount if something unlikely happens. So Pepsi had to pay $10 million. If the right thing happened during the game then Berkshire Hathaway would have paid a billion, and some lucky consumer would have walked away a newly minted billionaire.
Berkshire's General Re does reinsurance, not re-"reinsurance". Is there a recursive step -- Could General Re face a claim that it needs to leans on the rest of Berkshire to pay?
The article says its insurance companies face a 2 percent chance of being "$12 billion" insolvent, which Berkshire could cover from non-insurance profits. But would that still be true if the claims came in, or would the non-insurance companies also have correlated down years?
I suppose Berkshire Hathaway is big enough that if it came down to it, it could liquidate equity ($500B minus devaluation due to whatever catastrophe) to make good on claims.
No way that Berkshire pays a $500b claim. They would find a way to stick the US taxpayer with the bill as many smaller companies have done before them.
reinsurance is also a nice way to reduce a company's taxes, and to hold money offshore. Many reinsurance companies are owned by another company; but the "re" is incorporated in a low or no tax jurisdiction such as Cayman Islands or Bermuda.
Hurricane Katrina (2005) was up at 160 Billion and Harvey (2017) hit 125 billion. So 400 Billion is just at the upper end of the expected range.