“We’re not going in for the free music around here,” Bono joked on stage. Apple didn’t pay a traditional wholesale price for each of the 500 million albums. Instead the company paid Universal and U2 an undisclosed lump sum for the exclusive window to distribute the album. Universal plans to piggyback on the big push for “Songs of Innocence” to promote the band’s 12 older albums, a critical factor for a veteran rock band. The band’s recent albums have shown a steady decline in sales even steeper than the overall industry trend. “No Line on the Horizon,” from 2009, has sold 1.1 million copies in the U.S., according to Nielsen SoundScan. That’s down from 3.3 million copies for “How to Dismantle an Atomic Bomb,” and 4.4 million copies for “All That You Can’t Leave Behind,” released in 2000.