Most people buy $200 iPhones with massive monthly bills, at least in the US. I don't know if that changed yet.
I mean, I don't have any data, feel free to prove me wrong. But when I was a poor student, I wouldn't even dream of buying a smartphone outright, yet alone an iPhone.
And I had a look, those $6/month contracts barely subsidise anything. I don't really get what's relevant about them.