Ask HN: Any indie mobile app developers doing consistently well?

So I'm having a bit of a hard time keeping my income stream up. I have a couple of kids iOS apps that were once making me around $100/day near launch but fall to $30/day or less and continue falling each week.

App distribution is so dependent on app store rankings. In terms of marketing, I don't know of any cost effective ways to promote my apps. The way apps are found and downloaded is just so segregated from the outside world, its not like web marketing at all.

Anyone have advice or experience to share? Thanks