Let me say that we've been very lucky, and we know it.
100sounds has been in the paid Top 100 (and even reached #33 at its peak) since just before Christmas (the app was released 12/12/2008).
As one developer said in USA Today:
"People fight really hard to make the list," says British developer Mark Terry, whose Band music application has been at the top of the charts since its July debut. "If you're No. 102, you don't exist."
Being in the Top 25 is key because your app is viewable within the AppStore app, and to a lesser degree the Top 50. Top 100 for viewing in iTunes' on your PC or Mac. Re sales figures, Top 100 would probably average 500/day and Top 50 probably twice that. Our best days were just over 2,000 (Christmas, Dec 26th, and one other day).
We realize our success is the exception, and we owe a lot to the MacRumors community, where we first posted promo codes (we have more... just post telling us how you'd use the app) and earned our first reviews, etc. That's why we're giving back with our $1,000 iTunes Giveaway!
I will be writing about our experience in
iPhone Life Magazine (I'm a Contributing Editor), from the makers of Smartphone Magazine. I will probably included more specific sales figures there, but I can tell you the trends have been quite interesting. For example, weekends are busier than weekdays. Christmas and the next day were huge. Inauguration day was very slow (everyone watching TV, etc.).
Lately, we're slipping (#85 or so) so any plans to quit the day job are being revisited! It's been a great run, but as new apps are released, it's inevitable that they'll displace you. We've enhanced the app based on requests (more sounds, better quality, shake-to-play) but new apps, especially if Apple chooses to feature them, get all the buzz and that's powerful stuff.
We've done advertising (over $1,000/month) and a $1,000 iTunes giveaway ($10 just for
sending us a video showing how you use the app for practical use or practical jokes, plus a chance at some cool cases from OtterBox, Speck, or headphones and earbuds from ZAGG and iFrogz).
My recommendation, unless you can do it MUCH better, do NOT bother copying an app that's already out there. Odds are, twenty other developers are already doing that. As soon as iFart got some buzz, twenty more came out and did nothing remarkable in sales. I'm sure fifty Mafia apps are being writting now. You're better off coming up with something creative that can get some buzz, either from Apple or one of the various news sites/blogs.
I'd be happy to share more thoughts, and again I plan to write a regular column on the topic, in the printed version of iPhone Life.