Approximately 70 new iPhone apps are added every day

"There are, as of Monday, 10,215 applications in the app store. The store is adding about 70 or so new applications every day.
Of those apps, about 3,500 of them are games (games and entertainment categories). The average price is $3.13 with $0.99 being the most common price. Interesting how this has fallen over the past few months.
It would cost almost $32,000 to buy every single app in the app store, but you would only be able to install 148 of them at a time. The least popular category is Weather with only 52 apps thus far.
A the current pace, the iTunes App Store should hit 25,000 applications sometime around the 1 year anniversary of July 11, 2009."
Source: 148apps blog, 29th November 2008, pre-empting Apple's announcement of 10,000 applications