to judge the viability of developing these much ballyhooed "apps on devices"? I came across a few numbers recently ( Aug 28,2010 )...here's the link to the page:
http://www.electronista.com/articles/10/08/28/apple.passes.quarter.million.app.mark/

Here's an older page:
http://tech.fortune.cnn.com/2009/05/15/pushing-the-app-store-price-envelope/

Interesting, 97 percent of apps on Apples App Store are priced uner $10 US, and the overall average price is $2.67. Apple gets 30 percent, leaves the developer $1.87. Without any statitics for actual number of downloads, one can only make a guess. Let's say your app is "average", and does pretty good and gets 10,000 downloads. Your "gross" is $18,700, out of which you take your cost to develop the app, testing time, bug-tracking, updates...doesn't really make for a "get rich quick" idea, does it? To make matters worse, roughly 25% of apps are free, and 67% are priced less than $1, so there's a good chance your competition might be "good enough" to bite into your sales, or at least coerce you to lower your price from the average to $1, then you'll get only 70 cents per download. Now, 70 cents x 10,000 (since Apple keeps 30 percent!) and for the year you just earned $7000!
I'm just not convinced...these types of numbers mean you'll have to develop what, like 7 or more apps just to earn a somewhat reasonable living?
(edit-typo error on $7000 above)