$16 doesn't sound huge to you because you are living in a bubble.
It is for everyone that has is bank account in the red for half of their month. Which is a lot of people regardless if they live in a developing country or not. And those that can save money do not necessarily save money for a smartphone. They do it for their own financial safety. Even the streaming accounts are usually shared accross friends and families and said services don't crack down on them because they know they would simply lose their customers completely anyway. They would rather keep money in case their home need a reparation or their car they are using to go to work break down.
So when the time comes that their phone has issue, many of them are faced with a non scheduled financial issue. They will definitely repair their phone if it is more affordable than buying a new one. No wonder their are lots of repairing phones shops in every city. Where I live you can literally see a queue on the sidewalk during the opening hours. The alternative would be buying a second hand cell phone with the risk of ending up with one whose battery is already in average conditions.
> That's $16 per month. Easily affordable for most of developing world.
This argument sounds a lot like a used car salesman.
I think focusing on the monthly payment is deceptive. Especially with a device like a phone which could easily meet its doom before the 5.2 years used in your calculation are up.
It's reasonable to compare the total cost of ownership or the up front price. Your choice is a $1000 phone or (say) a $600 phone (new iPhone 14, no tax). There's $400 difference there. That's your money making the choice.
The question of whether it's worth it is something else.
$16 a month is close to the cost of financing a basic motorbike over its expected lifetime. People in developing world mostly drive 125/150 cc and expected lifetime is ~10 years
To me it seems like throwing money out of the window just for the sake of it.