I can't say that either of us represent the majority of smartphone users, but I find it interesting that my wife and I have different approaches:
I'll almost always shop by screenshots. If an app looks hideous, I'll assume it was created by slovenly, hateful people and pass on it. If it looks lovingly crafted, I'll try it. As the latter will usually be a paid app, this again reinforces the idea that someone has put some effort into it.
My wife, however, will just get the cheapest app. In fact, she'll get several free ones. Right now she has about five different pregnancy apps, all free. She's generally of the camp that argues that there's always going to be a free app that does the same thing, so she rarely pays for apps.
Now I'm pretty sure there are more people in the world like my wife. But I'm also sure that developers are making vastly more money out of people like me. But who knows.