qnli question: How much did advertisers spend for a 30 second ad spot during American Idol in 2014? sentence: American Idol became the most expensive series on broadcast networks for advertisers starting season four, and by the next season, it had broken the record in advertising rate for a regularly scheduled prime-time network series, selling over $700,000 for a 30-seconds slot, and reaching up to $1.3 million for the finale.