Apple said that by the end of this month developers will have earned “over US$4 billion cumulatively” from sales via its App Store, including more than US$700 million in the quarter to the end of December 2011 alone.

Taking into account the company’s 30 percent share of sales, this would indicate that total App Store revenue has passed US$5.7 billion – with Apple keeping US$1.7 billion of this. The company said in July 2011 it had paid out more than US$2.5 billion to developers.

Numerous metrics companies have noted that sales of apps for Apple products were boosted by the introduction of the iPhone 4S in the last quarter of 2011. Prior to this, numbers had been on the slide.

In the company’s results conference call this week, Peter Oppenheimer, Apple’s CFO (pictured), said that the App Store now has more than 550,000 apps available, including 170,000 specifically for the iPad.