Apple revealed earlier this week that its iTunes music store is now home to 575 million users. Horace Dediu of Asymco noted that the company is adding roughly a half-million new accounts on average per day. At its current rate, Apple will add another 100 million iTunes accounts by the end of 2013. The analyst found that while more consumers are using the service, revenue per account has actually decreased over the past few years. He explained that each of the 575 million accounts generates about half as much revenue, or $3.20 per month, as Apple’s 100 million iTunes accounts did in 2009.¬†Dediu doesn’t think Apple is in trouble, however. He notes that customer satisfaction and loyalty is still high, and the number of new customers is increasing at higher rate than the decline in spending.