David Barnard looks at Sparrow’s rankings in the App Store, compares them to his own experience selling apps, and makes the case that despite how popular and well-liked Sparrow was it wasn’t making enough money to sustain their 5-person team and give a return to their investors:

The age of selling software to users at a fixed, one-time price is coming to an end. It’s just not sustainable at the absurdly low price points users have come to expect. Sure, independent developers may scrap it out one app at a time, and some may even do quite well and be the exception to the rule, but I don’t think Sparrow would have sold-out if the team — and their investors — believed they could build a substantially profitable company on their own.

The Sparrow Problem