Google may have plenty of reasons to be proud of its Android operating system, but when it comes to the Android ecosystem, another company may actually be having more success selling Android apps than Google is.

That company is Amazon, which last year launched its own Android app store, dubbed Amazon Appstore.

As detailed in a recent report from analytics firm Flurry, when looking at a “basket of top apps”, the Amazon Appstore versions did far better than their Google Play (formerly Android Market) counterparts. On average, for every $1 spent on the iOS version of an app, the Amazon Appstore version pulled in 89 cents compared to just 23 cents for the Google Play version.

A big part of Amazon’s success hawking apps is the Kindle Fire, which has fast become the most popular Android-based tablet. Fire owners, of course, purchase their apps through the Amazon Appstore, not Google Play, so Google effectively earns no app revenue from the top Android tablet. With this in mind, it’s no wonder that Google is reportedly working on a tablet of its own with some urgency.

Now Amazon is looking to add insult to injury by cashing in even more with its app store by adding in-app purchasing and subscriptions. Bloomberg’s Danielle Kucera has the details:

The service being tested allows both subscriptions and purchases of individual items within apps, according to Maria Ly, co-founder of Skimble Inc., a seller of physical fitness programs that has been involved in Amazon’s pilot for about a month. Sally Fouts, a spokeswoman for Seattle-based Amazon, declined to comment.

According to Kucera, “Amazon plans to charge a 30 percent commission to clients for its in-app purchase service, the same rate as it charges developers for app sales.”

With Amazon reportedly prepping new Kindle Fire models and in-app purchasing expected to generate more than a billion dollars in revenue this year, it’s not surprising that Amazon is looking to roll out in-app purchasing and subscriptions functionality. Both could not only be crucial to maximizing revenue earned from Kindle Fire owners, but to increasing the number of developers interested in distributing their apps via the Amazon Appstore.

That’s important because right now, Amazon may be selling apps more effectively than Google, but it has a lot fewer of them. As Bloomberg’s Kucera notes, the Amazon Appstore only has 1,400 apps compared to over 450,000 available through Google Play. While there’s something to be said for a quality-over-quantity approach, if Amazon is really going to take advantage of the opportunities the Kindle Fire is giving it, luring developers to the Amazon Appstore and giving them the ability to monetize their apps through in-app purchases and subscriptions is a must.