Fox also bid $1.5 billion for the 2014 and the 2016 Olympics.

Brian L. Roberts, the chairman and chief executive of Comcast, said that spreading costs over four Olympics was critical to the bid, which was divided in two: $2 billion for the 2014 and 2016 Games, and $2.38 billion for the next two, whose locations have not been selected. NBC paid $2 billion for last year’s Winter Games in Vancouver (and lost $223 million) and next year’s Summer Games in London.

“We’ve said all along that we’d take a disciplined approach, where we could take a path to profitability,” Roberts said in a conference call. “It was responsible.”

Still, Comcast is paying considerably more than Fox to keep the Olympics in the NBC family than General Electric did for the Vancouver and the London Games. Neal Pilson, a former CBS Sports president, said, “I think Brian felt some pressure to validate the merger, and I think this also establishes that, as everyone felt, the Olympics were more important to NBC than they were to any other network.”

ESPN and Fox bid as if they did not feel they had to win the auction. In a statement, ESPN said: “We made a disciplined bid that would have brought tremendous value to the Olympics and would have been profitable for our company. To go any further would not have made good business sense for us.”

Craig Moffett, an analyst at Sanford C. Bernstein, said Comcast’s winning bid was out of character for a company that has been “relatively cautious.” But, he added: “I think it’s fair to say that at this price, the Olympics are going to be a loss leader for Comcast and they will have a negative effect on short-term earnings. Still, strategically, it’s possible they can pay for themselves.”