Marco Arment just posted the finances for his podcasting app, Overcast. The numbers are very good, and at first glance very encouraging for independent developers. But when you look at the size of Marco's audience, the numbers aren't surprising at all.
Can Louis C.K. sell a comedy special for $5 on his website and have it be a success? Of course. Louis has one of the biggest audiences in comedy, and he sold over 110,000 copies in four days the first time he tried this distribution method. Could a fledgling comedian record a comedy special and try to sell it on their website for $5? Sure, but it probably won't make much money regardless of how funny it is.
When Marco releases an app to his audience, chances are that it will go well. This is not to detract from Overcast – it's a great app. But when you consider that the number of in-app purchases (46,940) is only about 60% of the number of followers Marco has on Twitter (~78,014), the numbers look very different. Not to mention the audience that his blog and podcast have. I am not trying to slight Marco – building an audience is as hard, if not harder, than building a fantastic app. And doing both at the same time is like the Ironman of independent software development.
That's also not to say that these numbers aren't encouraging or reproducible. Because the truth is anyone can build an audience, just like anyone can build a great app. It just takes years and years of hard work and patience.
p.s. I'd love to meet you on Twitter.