Recently, we've seen a big trend of apps on the App Store going free because free apps tend to garner more attention and downloads (and in-app purchases mean that there's still a possibility of making a profit down the line). However, it turns out that there is one benefit of sticking with a paid app: they stay on the top of the charts for a longer period of time. Data (provided by a company called Distimo) for the month of May in the App Store shows that paid apps are "stickier" on the App Store charts; while free apps only lasted a little over a week, some paid apps stayed on the top of the charts for over a hundred days.
Why is this? My guess is that it involves something that we've heard a lot of talk about, which is that the habits of paying customers are different from those of "free app" customers. Customers who pay for apps are more likely to leave thoughtful reviews and spread the word about a worthwhile app, both of which will extend the time that an app is popular. Customers who use a lot of free apps tend to buy and dispose of apps quickly, while customers who pay are more likely to find the ones they like and stick with them for a while.
After all of the big news about free apps, it's interesting to hear that there are still reasons to stick with paid. As the App Store continues to develop, there are multiple working models for software sales unfolding.