A: 21,000 units in one week, thanks to being an Amazon.com daily special. The 99 Most Essential Beethoven Masterpieces landed at #29 on Billboard's album chart. If I recall correctly, the album made it to #1 on Amazon.com's MP3 album chart. Normally the album download, which has 99 full tracks, sells at Amazon.com for $7.99 (still a bargain considering the amount of music).

Many of Amazon.com's best selling album downloads are either the daily specials -- which tend to sell for $0.99 to $2.99 -- or one of its weekly $5 sale titles. It's evidence that customers will react to short-term and very cheap deals. If iTunes offered such deals, an album could really fly up the chart. If Amazon.com can help an album move 21,000 units in a week -- granted, it was around Christmas time -- iTunes could easily push one past 100,000.