Again, that is not how it works.
The price is set before any returns happen.
The less than 1% of people doing frequent returns is not why the iPhone costs what it does. Even if there were no return policy, the phones would still be expensive.
As for environmental impacts... why are we blaming the returning consumers, and not Apple for releasing a phone every year?
And why are we singling out phones?
People also return a lot of other things. Should people not return food that is bad or they didn't like because "someone else wanted it" or "the environmental impacts of them making you a new meal"? Of course not, if your food is bad you send it back.
If your phone isn't what you wanted, you send it back.
If your grocery order had something that wasn't what you wanted/needed, you send it back.
If you buy new clothes and they don't fit or are a different color than they looked online, you return them.
Come-on now, this is a non-issue.