Edward Kim has blogged about his experiences with his app Car Locator, after placing 3rd in his category in the ADC2 and being featured in the Android Market.
He says he was making $80-100/day off the app before it was featured. Being featured bumped this up to about $435/day. Now, I'd heard that being featured by Apple in the iTunes store can vault your app into massive numbers, but until now I hadn't heard about any comparable effect in the Android Market. Being featured more than quadrupled his daily revenue, so I'd say that's a pretty nice effect. It does make sense, since the featured apps are the very first thing you see when you open the Android Market app.
None of my apps has been featured by Google, but PetBook did get featured in T-Mobile's Top Picks. Then I only had a free version, and I've struggled with complaints from some users regarding information being saved properly and the photo gallery working right. Here's a graphic of my usage stats for PetBook, and the bump I got from T-Mobile near the end of January (that second bump is from releasing an update).
Around the time of the first peak, I had two $9.00 days from the advertising in PetBook, but within a week I was back down to the norm of about $0.75/day. It would have been interesting to see if I had an active paid version whether that would have translated into some really nice sales, but oh well.
The temporary boost was nice, but apparently nowhere near being featured in the main Android Market. Maybe someday...
Anyway, congrats to Edward. He encourages devs interested in mobile app development to give Android a try. More awareness of success stories is going to lead to much more interest in the platform. I'm generating a very nice income myself...not up to $13K a month, yet, but definitely a self-sustaining income. So it can definitely be done.