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 prices 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 gold rush is well and truly over.
Ok, so the market matures. Just because the gold rush if over, that doesn't mean selling software at fixed price is over. It just depends on the product. A photo app doesn't require any upkeep, while an RSS reader requires a server that needs to be maintained. Cross-platform apps require even more upkeep, and B2B apps need proper support and service to back up the technical side.
And many crappy apps simply aren't worth anything. Especially looking at Google Play, there are lots of solo developers with 100+ apps. Those are likely not very good apps worth paying for, in the same way that nobody will pay for a website I throw together in a few hours.
It's a complex market that's slowly maturing, and I don't think it's economy can be summarized in a simple statement like "the gold rush is over". Thinking about Warren Buffet's "be greedy when others are fearful", maybe this is just the right time to build something?