A Good Idea – Complete My Album
What a good idea! Apple tweaked the buying policy at the iTunes Store allowing customers to complete their albums if they previously purchased singles from that album. Instead of buying a single, only to go back and purchase the entire album, the rest of the album can be bought at a prorated cost.
If you fell into this situation within the past 180 days, Apple has a retroactive offer for your purchases.
Makes sense!
Update: Got an email from iTunes that says:
You have up to six months after first downloading a song from an eligible album to purchase the remainder of the album.