A study backing up my previous post - freemium model can make money if you have a monetizing strategy.
According to a BII analysis of App Store data, 93 percent of the top 100 grossing iPhone apps use in-app commerce. Of those 100 grossing apps, two-thirds are free.
As most the top grossing apps are games, in-app commerce is most commonly used to sell in-game currency. However, companies like Pandora and eHarmony are using in-app purchasing to sell subscriptions, while Marvel is using it to sell access to comics.