What happens everywhere, they go find something else to do. And the odds of that being ethically better go up as fewer at the top order from unethical suppliers.
Current failings of our world are not excuses not to improve it, or to be better people.
On another note, a personal attack is not appreciated here, regardless of where I work. Your comment history is rich with these types of things. We are happy to have you here, but please think about contributing more constructively.
Lets assume it costs more to make a job ethical (fewer hours, higher pay etc) - otherwise why not do it now? This means higher prices for consumers, so they now buy fewer products. This means less products need to be produced, so fewer persons are employed in making these ethical products. What happens with the workers who are now redundant?
Concretely, if an iPhone is replaced on average every other year but goes up 30% to the the ePhone (ethical phone) it is now only replaced every 3 years. This means fewer ephones are produced, which means that roughly 1/3 of the workforce is no longer required. What are those 1/3 to do?
The question here is really "Do they have the resources to move to where the work is?" Immigration to work better and earn more, whether temporarily or permanently, has been happening since transportation became a thing. Go to Dubai and see how many Pakistanis are doing jobs there. Or look in the average American commercial kitchen and count the Mexican and other latino immigrants.
Almost everyone in America is a descendant of immigrants, for that matter. In many cases, those immigrants were fleeing violence and persecution, their passage paid by overlords who felt it was very decent and moral of them to ship the people overseas rather than just killing them off (i.e. the Irish in America).
Those help, yes. Not absolutely necessary, though - every wealthy country in the world relies on illegal immigrants. Transportation is more of an issue (and can itself turn into a form of indentured servitude).
Current failings of our world are not excuses not to improve it, or to be better people.
On another note, a personal attack is not appreciated here, regardless of where I work. Your comment history is rich with these types of things. We are happy to have you here, but please think about contributing more constructively.