Economists would disagree with this.
You need to have a high end and a low end. The low end features needs to be low enough that people who want high end features see no reason to buy the low end phone. The low end has to be good enough that people feel like they got a good deal regardless of the price.
The difference in cost to make each model isn't much, but if the camera is the same on both phones, most people would simply buy the lower cost phone, reducing Apple's margins.
Another example. Third class seats on the train. They aren't comfy, not because they are low cost. They are designed so people who can afford first or second class tickets see no reason to take a third class seat, which is meant to provide a low cost solution to people who can't afford a first or second class ticket. It gets more people of all classes, on the train.
