The last I heard, NBC don't actually pay a penny for their NHL rights. It may have changed, but it certainly used to be the case.
That hasn't been the case for a while, the contract that is in place right now started in 2011 and is a 10-year deal for $2 billion dollars that has NBC paying the NHL about $200 million a year. The deal before that had NBC paying the NHL roughly $17 million a year, though I'm not sure when that one started. The deal you are thinking of was back from 2004 and lasted 2-4 years, I can't find specifics though.