When is 30 seconds worth $5m? That is the question facing Super Bowl advertisers as they gear up for February 7, the biggest day in US marketing. The price tag that broadcaster CBS is charging for a television commercial for this year’s National Football League championship game is double the average $2.5m price a decade ago, according to Kantar Media. But the game regularly breaks US TV viewing records, with 114m people tuning in last year. This Sunday’s pie will be even bigger, as CBS will for the first time make its livestream of the game and all national commercials available over internet TV boxes including Apple TV and Roku. Advertisers are already teasing their ads well before game day, using digital channels to extend their reach.