I own more than 1,000 CDs, and I buy new music almost every week. I will often now buy single songs for 99 cents through iTunes, especially when I want to listen to a song right away, and not wait to buy the CD, or when I might only like one song on a CD.
Yesterday, I did something new for the first time: I bought an entire CD through iTunes Store for $9.99, it was Diana Krall's new CD "From This Moment On." Normally I would prefer to own a physical copy of the CD to have the liner notes, and have a physical copy of the CD for my library. The CD is available for sale on Amazon.com for $10.88, and I would usually be willing to pay $1.89 extra to get the CD compared to downloading from iTunes store.
However, buying the CD from Amazon involves: a) shipping (unless you order about $50 to qualify for free shipping), and b) waiting up to a week to get the CD, two costs that I would typically be willing to pay. But what convinced me to buy and download the online version of the CD this time: ONE BONUS TRACK, only available when you download the CD, and NOT available when you buy the CD in a store or online through Amazon.
Brilliant marketing strategy!