Smartphone apps are big business, with millions downloaded every day around the world. But most apps are free (or really cheap); so how do business make money off them? One reason: In-app purchases.
From extra lives in games to subscriptions to favorite magazines, app developers can build in all sorts of ways to tempt you into spending more money.
How well are their efforts working - and how can you resist the urge to overspend when using "freemium" apps?