Who are the "robber barrons" in this case, and how did they cause "the right situation where the people have no choice"?

I originally wrote a long reply, but I'll just say that I don't buy your framing, and I don't think the people who depend on that foreign money flowing in to pay them for their work at the prevailing wage where they live agree with you either.

They are not slaves, they are free to quit and work somewhere else. Are they not?

Right... so the line goes. They're free to go to any neighbouring city that will do the same to them now that we've destroyed the village (by poaching young people in various ways. There are many ways to destroy a city if you are strategic and have financing.)

In these countries the cities are created around the factories etc and planned as part of the development.

You're not free once your subsistence relies on this corporation. It's slavery but because some tokens are being transferred (the food supply is probably also corp. owned--especially in the early stages of the development) it is possible to fool the naive / stupid into think this is not slavery.

What if the alternative to these jobs is not other jobs, but no jobs? If working in such a job is considered slavery, then most of the west also employs slaves in the form of "simple, low skilled" jobs, such as cashiers. Many people don't have many options, and losing even such a job could mean unemployment.