Gannett's Wisconsin papers will begin offer free ads for an increase in an advertiser's buy. 

This story from Editor and Publisher: 

"Effective today through mid-October, if a current advertiser increases the media buy by 25%, the paper will double the entire run for free. A similar program exists for new advertisers."

E&P describes this as giving away advertising. My guess is that advertisers would describe it as 50% off.