So say I don't buy the iPhone because I consider it unethical to pay only $100, but since I don't actually need a new phone, I'm not going to pay $200+. The seller dies because they were $100 short of some essential medicine they needed, or whatever. Is this really the outcome you want to see?
In an ideal world, I would just pay the person $100 and not take their phone—but, c'mon, this isn't the world we're living in. People die every day in the US—never mind the rest of the world—because they couldn't afford medicine/shelter/food/etc
You're contriving a situation where the seller doesn't have any other options AND you also don't have any ability to buy it to later sell at a profit (which would give the seller the ability to negotiate a better price than $100 with you while still allowing you a reasonable profit when you sell it).
I agree you can contrive a situation where the best ethical option is to pay the seller $100 for the phone but you really have to work on it (and the situation is pretty contrived to begin with)
In an ideal world, I would just pay the person $100 and not take their phone—but, c'mon, this isn't the world we're living in. People die every day in the US—never mind the rest of the world—because they couldn't afford medicine/shelter/food/etc