And it makes sense, because an iPhone is a fairly inexpensive luxury good. Certainly, it's cheaper than a comparably high end purse, car or house. And, in the US, it's heavily subsidized by carriers.
Yes you pay less upfront, but in exchange for paying more on your monthly phone bill. Less of a subsidy and more of a payment plan.
The free phones aren't going to be the latest generation, but they often have partial subsidization when you switch, like maybe half the cost.
I'm sure a lot of people are frustrated by food costs, and have adjusted their food purchasing decisions, while also buying new iPhones.
At $1.5 per day for the latest iPhone+AppleCare, the upgrade program made me realize I get at least $5-$10 of value out of my phone daily. Even in just time saved on daily tasks e.g. banking, shopping, taxis, work (I don't have to walk to the "location" or even to my desktop).
Context: For a long time I stayed on my iPhone 6, trying to extract every last bit of value from it (replaced the screen 1x and the battery 2x) before it was no longer getting updates (I had it 6 years).
1. The cognitive overhead of trying to extract every last dollar is greater than $1 a day. In the back of my mind I kept going back and forth, do I upgrade the battery again, or switch to a newer $1000 phone? If I include the time and money ($100 every 2 years - $0.14 per day for the battery; $150 every 3 yeas - $0.14 per day for the screen) actually spent getting the phone fixed, then the upgrade program is a no brainer winner.
2. The improvements were noticeable! Significantly. When I got my iPhone 11 Pro after giving away my iPhone 6, my laptop usage reduced by 75% (I had been thinking of buying a new laptop - the iPhone purchase saved me money overall).
3. I stayed on my iPhone 6 because "I just didn't believe X, Y, or Z was actually worth the upgrade". For $1.5 per day (vs $0.3) for a tool able to save me $5-10 per day, every day, why ever lag behind? What if the 14 is able to save me $15 per day because of X, Y, or Z but "I just don't believe it" and miss out on years worth of "savings".
4. Even without everything I've said prior, I can afford the $1.5 per day, even for frivolous reasons. When my iPhone, a tool, costs the same as one bubble tea / fancy latte a week, I'd rather reduce my cafe visits slightly and use the best version of the tools that are known to improve my life.
5. There is still a lot more iPhones can improve on, and I would like them to improve. I specifically also buy the Pro because I view "giving Apple that margin" as a "vote with my wallet" that there is a market for a more feature-rich iPhone can do next year and the more my vote counts.