Most people I know buy with the same discretion as everything else. I rarely buy apps, the only time I do is if I have a specific need, and usually there are plenty of reviews for most of the Apps. Of the 100 or so apps I have on my iPad, I might have paid for 5 or 6, ones like Paperdesk that I use for note taking and such. And you know what? Nearly every one I bought had a limited 'lite' edition so I could try it out, I could hardly say that it has caused me to be less frugal than I already am.
Chances are the people blowing hundreds on Apps they actually don't want or need walk through life in much the same way. Go to the mall sometime, you'll see what I mean.
And you know what, who cares? The economy is in the toilet, we need industries that are lucrative. I know of one laid off software engineer who is feeding his family based on iPhone apps he sells. He isn't an overnight millionaire or anything, but that combined with his severance pay and an odd job or two has kept him from having to leave his house or stop eating for a week. That's how capitalism works, like Barnum said, "There's a sucker born every minute". Get behind someone in line at the grocery store buying food using food stamps, then spending $100 on Alcohol. THATS a problem in this society. Plenty of people drink themselves out of house and home, that among alot of other things are real problems in this day and age. And while I'm sure it could happen, I really don't think alot of people are buying apps out of house and home. Alot of it is gift cards and teenagers with liquid income, most people who buy the apps, can afford it. Sure, you can look at the big picture and say "$27 Billion in revenue on Apps", but you could also look at the fact that the market share is so massive, that's only a few bucks per person. Remember the guy who filled his iPod the day it came out with music bought off of iTunes? As in, he bought enough $0.99 songs on iTunes to fill up a 5GB hard drive, in one day. That was what, 2001? And you know what? I'm sure he could afford it, so all the more power to him.
-John