[sp332]

Morally, Facebook would realize that it has all the power in this situation and use its position to act for the good of everyone involved. Squeezing an employee to see how little you can get away with paying them, especially when this makes their living conditions much worse, is immoral.

[tyingq]

I doubt that the contract FB has with the cafeteria services provider specifies individual wages, or even the number and type of positions.

It is more likely specifying things like how many people they have to feed, standards around variety of food, selection, etc.