As the ads showing in the New York Times and the Wall Street Journal, Apple said users have “downloaded over 300 million” applications from its App Store since it opened in July, 2008. Apple also informs that there are now over 10,000 apps available for iPhone and iPod Touch on the store.

Though according to Apple most downloads are free apps, Dan Frommer, Silicon Valley Insider, estimated that “Apple has booked $50 million to $100 million in revenue so from those sales.” Here is how he came to that numbers:

• Apple has told the WSJ that “most” iPhone downloads are free apps. We don’t know how many those are, so let’s assume they’re about two-thirds of the downloads.
• That suggests that 100 million downloads (of 300 million) were paid apps.
• Apple recently published the top 10 most-downloaded paid apps. Their average price is about $2.80. We’ll round that up to $3.
• That suggests Apple’s gross revenue from paid apps is $300 million.
• Apple takes a 30% cut, and gives 70% to developers. That’s $90 million for Apple, which we’ll round up to $100 million for simplicity’s sake.
• But this may be overstate the reality. In August, Steve Jobs told the WSJ that Apple made $30 million in gross sales for the first 60 million app downloads. Five times that (300 million downloads at that same rate) is $150 million, of which Apple would get 30%, or $45 million. We’ll round that up to $50 million.

“More important is that Apple’s app platform is still far ahead of its competition. And we think it’s doing its real job, too: Helping Apple sell more iPhones and iPod touches,” said Dan Frommer.