A $600 iPhone is probably one of the best investments you can make if you want to participate in modern society.

Agreed. And iPhones have been around for like a decade and over a billion of them have been produced, so there are plenty of cheap used versions available.

A $150 iPhone 5S is likely a better choice for someone in the bottom 1/10th of wealth.

Want to do a survey of how many people in that bottom tenth have faced massive out of pocket expenses for healthcare and insurance premiums?

iPhones are cheap when they are not purchased new.