Apple brags that more than a billion iPhone applications have been downloaded so far from its App Store, a successful online store of instantly installable iPhone software. But how much money has the App Store made for Apple?

The store, which offers both free and paid for-sale apps, nets Apple a 30 percent cut of all sales. Typical app prices run from 99 cents to $2.99, with a few priced higher.

Silicon Valley venture capitalist Jeremy Liew, an insider on technology business deals, has good reason to doubt industry analysts and Apple’s publicists on the success — or not — of the App Store. Liew number-crunched some public statistics and crafted an estimate .

Liew began with a survey conducted by tech book publisher O’Reilly in Sebastopol, Calif. "O’Reilly did a survey of iPhone apps and noted that the mean price for paid apps is $2.65," Liew wrote. "Multiplying this by 25-50 million paid apps, that suggests that the cumulative revenue from iPhone apps is around $70-$160 million. Apple gets 30% of this, so Apple has probably made around $20-45 million from the billion iPhone apps downloaded. It took six months to hit 500 million app downloads, and only three months for the next 500m app downloads, so Appleā€™s revenue run rate is higher than this."

To many companies, $20 million would be reason to break out the champagne. But Liew put the figure into context for Apple, which collected nearly $5 billion in revenue last year, much of it from $400 iPhones (The company has since cut the entry level price to $199.) "Given that Apple sold 13.7 million iPhones in 2008," Liew concluded, "the App store is not a meaningful direct contributor to their overall revenue. Much like iTunes, Apple is using the App Store to drive demand for their hardware."