Apple has introduced the “Complete My Album” feature on its iTunes Store which gives a full credit of 99 cents for every track the user previously purchased and applies it toward the purchase of the complete album. For instance, most albums on iTunes cost $9.99 so a customer who already bought three tracks can download the rest of the album for $7.02, previously they would be charged the full price.
It’s about time, but of course there is a catch. The offer to purchase the rest of the album at a "discount" will only be available for 6 months after the purchase of the song(s). Still, that’s not so bad, as many people would likely purchase the album before that time frame anyway.
Source: Neowin