Last week, in a release, Apple boasted that their App Store had just topped 15 billion downloads, a truly staggering figure. As part of that release they also stated that over $2.5 billion has been paid out to developers. Clearly, the Apple App Store is booming.

The future, according to data released today by investment firm Piper Jaffray, is looking even brighter for the company.

According to estimations, Apple will see a 61% increase in apps downloaded from their App Store in 2011. Specifically, that means that instead of 51 average app downloads per person (like they saw in 2010) that number will leap to 83 downloads per person.

If that’s the case, then the 20 billion download milestone is right around the corner. Fortune breaks down some of the other takeaways from the Piper Jaffray stats –

• More apps: The average iOS device owner will download 83 apps in 2011 vs. 51 in 2010, a 61% increase year over year. “Smartphone users are showing an increasing appetite to use apps to add features to their phones,” Munster writes, “and iOS has the leading app ecosystem.”
• More expensive apps: The ASP (average selling price) per app is rebounding. ASPs are up 14% y/y in 20111 vs. an 18% decline in 2010. “After the initial race to the bottom in App Store pricing,” says Munster, “we are seeing users pay up to add features and games to their iOS devices.”
• More apps than Android: Apple’s App Store has more than 425,000 apps. The Android Market has 200,000. In May, Google (GOOG) announced its 4.5 billionth app download, compared with Apple’s 15 billion as of July 7.
• Plenty of free apps. 82% of the apps in Apple’s store are free. The 18% that users have to pay for have an ASP of $1.44. According to Munster, the increase in ASP is driven by the more-expensive iPad apps that represent a growing percentage of app downloads.

Not only does this mean that Apple will be hitting App Store milestones more quickly, but it also is a great sign for the business model of the company as a whole. Even though App Store revenue only accounts for 1% of the company’s total revenue, they are “increasingly dependent on the health of [their] App Store.”

Makes sense. In order to rack up sales of iOS devices, people need to love the selection of apps that are available for said devices – and that seems to be the case.

In other App Store related news, a report released last week by analytics company Flurry suggested that the free to play or “freemium” gaming model is becoming the best option for developers.

In that report, they said that 65% of the revenue generated from the top 100 iOS games is now from freemium games. In that gaming model, users can download the gaming apps for free but are offered in-game purchases. Once they get hooked on the game, players can spend thousands of dollars on an app that was free in the beginning.

[Image Courtesy Wired]