On the Paul Lamere's blog (see previous article), one can read an interesting note about iTunes.

Reminder: iTunes is a proprietary digital media player application, launched by Apple Computer in 2001, for playing and organizing digital music and video files. The program is also an interface to manage the music on Apple's popular iPod digital audio player. Additionally, iTunes can connect to the iTunes Music Store (iTMS) which allows users to purchase digital music and movie files that can be played by iPods and iTunes.

The article reminds that Apple sold, during the first quarter of 2006, its 50 millionth iPod. Right around the same time, Apple celebrated selling its 1 billionth song on iTunes, considered as a big commercial success.
But is it really true? If we divide 1 billion by 50 million, we notice that only 20 songs on average were sold, by iPod. Therefore, after having spent $200 or $300 for a luxury walkman, an average person spends $20 to put music iTunes on it.

Lamere concludes: if this user buys 1 song per month, the credit card transaction fees have to be eating up any potential profits.