According to the independant, Apple does indeed get only 4 cts per track sold at 99cts ! Steve Jobs publicly said that the ITMS was a way for Apple to sell more Ipods and not to increase the company's margin. This cast a new light to the profitability of other online music stores without the Ipod to sell, such as Napster (rumored to be acquired by Amazon).
IMHO, this does not reflect the value brought by Apple to the music labels. What is striking is that record labels do make more money by selling downloadable tracks than by selling on physical CDs.
Maybe when Apple will sell, say 10 billion track per year, the bargaining power will reverse and Apple will get 50 cts ?