For commercial broadcasters, airing the Olympics means big money and big risk. I'm over in the US (before jetting in to Edinburgh) and watching the Olympics here has reinforced how high-value sport with a local hero can still bring in big money.

NBC paid a whopping $894m (£479m) for the rights to the Beijing Olympics and that's before the estimated $125m spent producing the event (including sending some 3,000 people to China). The good news for NBC is that the bet has paid off handsomely - thank to one guy in a swimming pool.

Ahead of the Olympics, NBC was able to sell $1bn of advertising across networks including Telemundo, USA, MSNBC, CNBC, Bravo and Oxygen; inserting a make-good clause if the audiences did not come.

But the broadcaster also had an ace in the hole; Michael Phelps. NBC astutely used its muscle to ensure the swimming finals were scheduled within US primetime and suddenly $894m looks cheap. By August 15, NBC had sold an extra $10m in advertising, with the top rate being $750,000 for a 30-second spot.

The broadcaster boasted record audiences - 114 million in the first two days (20 million more than Athens four years ago) and ratings have stayed strong (over 30 million) even on most non-Phelps days.

But some things can only happen in America. I watched NBC's coverage of Phelps winning gold no 7 by one one hundredth of a second and sat back to enjoy Britain's Rebecca Adlington attempt her own Olympic win in the next race. Becca was neck-and-neck in the 800m and things were getting tense when, guess what? NBC left for a commercial.

When the coverage resumed, we were treated to a resume of the amazing finish to Phelps's race. I did see Rebecca's moment of glory, but NBC was doing what it does best - maximising its investment and pushing its hero. The Olympics might preach Corinthian values, but who cares when Coca-Cola, McDonald's, Kodak and Visa are waiting in the wings?