Apple CEO Tim Cook greets the crowd with U2 singer Bono (2nd R) as The Edge (2nd L) and Larry Mullen Jr look on during an Apple special event at the Flint Center for the Performing Arts on September 9, 2014 in Cupertino, California.

'Songs of Innocence,' the band's latest release delivered for free, is firmly entrenched with 26 million customers downloading the set in its entirety.

U2 has gone from setting records to breaking them and, with the band's game-changing Apple partnership, simply defying all imaginable expectations.

So how did the album Songs of Innocence fare after being made available to 500 million people around the world as a free download on iTunes? No surprise here, scale pays off.

U2's Surprise 'Songs of Innocence': Album Review

Eddy Cue, Apple's senior VP of internet software and services, tells Billboard that U2's Songs of Innocence has racked up a staggering 26 million complete downloads since its Sept. 9 release as a free download exclusively to Apple's 500 million global iTunes customers. In total, Cue adds, over 81 million Apple customers experienced songs from Innocence, a global figure that includes plays and streams through iTunes, iTunes Radio and Beats Music. "To help put this into perspective," he says, "prior to this, 14 million customers had purchased music from U2 since the opening of the iTunes Store in 2003."

In a statement to Billboard, U2 said: "Apple is a tech company fighting to get musicians paid. The idea that they wanted to make a gift to the very people that actually purchase music is both beautiful and poetic, and for that we are very grateful."

Meanwhile, a physical deluxe edition of Songs of Innocence hits all other retailers Oct. 14, featuring 10 additional bonus tracks (unavailable on iTunes) including six acoustic versions of Innocence songs and four all-new cuts. Based on pre-orders alone, sources suggest to Billboard the physical deluxe edition will move an additional 70,000 copies in the U.S.

While U2's one-month iTunes deal is unprecedented in music retail, other recent experiments with "windowing," or exclusive release windows with a single retail partner, have produced surprising results in recent years. Jay Z's Magna Carta...Holy Grail was originally released as a five-day digital exclusive with Samsung's Galaxy phones, but that giveaway didn't cannibalize his first-week sales. Instead, the rapper sold an impressive 528,000 copies in its first full week at retail, besting the opening frames of his previous two studio releases. His wife Beyonce, who released her self-titled set as a one-week exclusive with iTunes on Dec. 13, sold 374,000 copies in its second week of release at all retailers (minus Amazon and Target, who protested Apple's surprise coup).

The U2 deal sets a new milestone in how recorded music is distributed -- and paid for. Not only did the band (and label Interscope, by association) net $100 million in free media exposure from Apple's global marketing campaign, Universal Music Group could have secured a $52 million payment for exclusive rights to the product, based on Billboard's estimates of standard label profit from 26 million album sales; alternately, Billboard estimates an upfront fee, excluding royalties, could be in the $5 million range. Reps for Apple and U2 declined to comment on deal terms.

The value of an ostensibly free album gets even more interesting when you look at eBay, where vinyl copies of the album have been selling for as much as $1,500. That's due to a Grammy-qualifying, white-label vinyl version issued to select stores on Sept. 30, the last day of eligibility for the 2015 Grammy broadcast. Just how limited was the pressing? According to the website for participating seller Looney Tunes in West Babylon, New York, only 300 were made available.