Here's a question: how come the top paid apps on average have higher ratings than top free apps? (
http://moby.to/dwvgvr)
I asked a marketing professor that I work for and he told me that his hypothesis was the level of thinking users did before they paid for something versus when they bought it for free was different. You probably want to make sure an app is worthwhile before you purchase it, by carefully considering its functionality, reading the reviews and so on. A free app doesn't elicit this kind of care before purchase. My professor said it was the same with student ratings: required courses tend to have poorer reviews than electives, partially due to the level of choice the student had in picking the course.
I agree to an extent, but there should be a counteracting force: feeling ripped off. Why should users feel so upset about a free app they downloaded that they would take the time to write a negative review, a review they probably didn't read before downloading themselves? Wouldn't users of paid apps feel more compelled to leave a negative review if they felt it wasn't worth the money? Thus, paid app users would probably be more incentivized to leave a negative review, even if they are less likely to feel negatively about the app.
Nonetheless, the empirical observation is that for the most downloaded apps, free apps are more poorly reviewed than paid apps. Might a third (decisive) factor be that app store shoppers are divided (generally) into extremely price sensitive and not price sensitive (meaning, free app buyers and paid app buyers)? This hypothesis might be supported by the fact that the free app reviews tend to have a different quality of language from paid app reviews (as you can read in the reddit article linked here). I personally feel that paid apps in general are of higher quality than free apps, so I think paying a small amount for apps, almost always (with the exception of Facebook, Twitter, Netflix, etc...), is worth the reduction in noise from sifting through free apps. My experience with these apps tends to be good, and I use the apps longer and download them less frequently then I might if I were a serial free app downloader (I think). The fact that free apps are more poorly reviewed doesn't help either.
The reason that it's important to understand these differences is that the decision to make it free or not might also be a marketing decision. Your goal with an app might be looking to make an in-app sale down the road to the user, to promote another product, or develop your brand as a developer. It could turn out that users in your target demographic don't "trust" free apps (in general) and thus don't download them, and you might harm your brand by offering them for free. You might also get a user base that doesn't understand your app before downloading, then leaves harsh negative reviews, thus also hurting your brand. Lastly, these users might be more likely to delete your app after a few days, and then move onto another free app, hurting your prospects of making a down-the-road sale or earning advertising revenues. Thoughts?