For a while now, developers looking to make serious money selling their apps were better off trying their luck at Apple’s (AAPL) App Store than with Google (GOOG) Play. But over at Tech-Thoughts, Sameer Singh has found some new data suggesting that in-app purchases are likely helping Google Play close the gap. Specifically, Singh looks at four different estimates for how much revenue iOS and Android apps generate on their respective app stores. While all four estimates varied widely in terms of how much total revenue each store generated, they also all clearly show Google Play apps increasing their revenues significantly over the past nine months. Singh writes that “if the revenue growth data is accurate, it does appear that the growth in in-app purchases has reduced the revenue gap between iOS and Google Play.”