It was shocking for me when I first encountered people who make $200K+ and didn't know where all the money went. I too presumed that being "savvy" was somehow linked with high income. I now know it is not that tight a binding.

Going back to iOS devices, they provide a simple filter. People who buy them pay more, and they are therefore likely to pay more again. It really says nothing about their income or credit card balance. It is purely about spending habits.