Credit:
Short version: not that much.
Long version: Anywhere between $20 and $45 million; when you count in LSVP's approximation that the ratio of free to paid apps, is somewhere between 1:15 and 1:40, and O'Reilly's estimate that the mean price for paid apps is $2.65. Multiply these numbers and you get revenue of $70-$160 million; Apple's 30%, which is how much they get from each sold application puts their chunk of the cake at $20-45 million.