Foxconn is not the municipal water supplier, the one you’d be dealing with if you don’t live in those barracks. Those high water bills are if you live in the “free” barracks, i.e. they’re fooling people into thinking the barracks are free (yay! I can keep all of my wages!) and then they’re getting billed for the shower by the litre or something. It’s scummy but TBH also quintessentially Chinese. Their roommates are probably telling them they’re stupid for believing Foxconn.
And if minimum wage doesn’t suffice to have your own regular apartment, with non-extortionary water prices – well, complain with the CCP. Though, I have to add as a smug European, working full-time and not being able to make rent is also very much a thing in the US.