Apple, at least, claims they don't make much money there.  Per their latest quarterly call:  "iTunes and App Store are still running 'a bit over break-even.' We’re investing a lot in these stores – that’s where the revenue is going."  <a href="http://www.techcrunch.com/2010/01/25/apple-q1-2010-results/" rel="nofollow">http://www.techcrunch.com/2010/01/25/apple-q1-2010-results/</a>