Berkshire isn't making big money on this.

Big money for his company these days is to generate a couple billion in profit off of a deal (eg the Bank of America, Goldman, GE deals).

The tiny premium this bet is likely to pay isn't worth getting out of bed in the morning for Buffett, except it was his idea and he likes to have fun with things of this sort. It's his version of a weekend golf bet (with the odds radically in his favor).