An iPhone 4 bought refurbished, then used gingerly for 2-3 years is within reach for many. Seen plenty of waiters and taxi drivers using iOS. It's not like they're all getting maxed out 6 Pluses every year.

If anything, one's phone is used so much that it's a reasonable thing to spend money on, even if you skimp on paying for data plans and spend less on other things.