How would that help those people though? Presumably these people are not forced to work in those factories, so just moving their jobs to robots in America isn't going to help them. It would only help them if the premium is going to the workers (and you could probably make do with less than $100: assuming that the workers get $5 of the $6.50, increasing the price of the phone by $100 and giving it to the workers would give them 20x additional salary).
In aggregate, this would result in fewer products being purchased and fewer jobs. That said, the conditions in these jobs appear to humane- with a few exceptions.
There are many organizations you can donate that $100 to instead. It may not make the world a better place for those specific people who assembled your particular iPhone but it'll make just as strong an impact someone's life.
