I have a few apps for Android. First few days you always get a lot of downloads (depending on what your app does). That was one year ago. I released another app a few weeks ago and the market has changed. Now, it's much more like the iPhone market where you fall into oblivion if you don't have some marketing strategy. Take a look at the 'just in' for all apps. It's filled with batches of 'hot babes' apps and skins apps so you fall down the list very quickly before anyone even has a chance to notice you.
I released a 'Sca', a spy camera app, a year ago and it's doing pretty well. Made $6,000 in 14 months. With the release of all the new phones this year, revenue has picked up to where I consistently get $30 per day after Google takes its cut. I tried $2.95, $9.95, and I settled on the current $5.95. Revenue is constant across all price points. There's no way to scoop up all price points, though, which is annoying. Anyone have any ideas for that?
Last I checked, you get bumped back to the top of the 'just in' list if you submit an update and it's been a few weeks since your last update, so it's a good way to spike up traffic.
I released a niche app for astronomy, Iridium Flares, that sells for $1.45 and makes one sale every few days.
I made sure my two paid apps have a free version. I have a few free apps that advertise my paid apps.
If you compare the top paid apps with the top paid games, it looks like there are more successful games than successful apps. People will pay for entertainment, but games usually require many more hours of work.