#2 Having a large labor supply suggests the job is competitive. However, even if that's the case having people constantly quit increases training costs.
The point of all of this is industrialization tends to follow a path where people move from terrible low wage jobs to more well paid work. Even China has moved past the first rung of the ladder with market forces forcing factory's to increase pay and or improve conditions. Presumably where going to run out of 3rd world countries at some point, though there is some concern robots / AI is going to end up filling that nitch possibly stranding a few countries.
China has absolutely not moved past the first rung of this ladder. The majority of the Chinese population lives in abject rural poverty.
[0] http://www.bloomberg.com/news/2012-01-17/china-urban-populat...
Most Chinese in the city (some which you may judge as living in abject poverty), are actually pretty happy with their situation. Even the homeless people seem more content than over here in Germany (I've talked to quite some of them over some baijiu at the corner of the street).
Please stop painting China a some kind of post-communist hellhole where people are starving on the streets whilst toiling away in backstreet sweatshops. You're not doing the country any justice, and you should really visit it someday.s
1. Quitting means you are no longer making money, and if that was an acceptable endgame then you likely wouldn't be employed in such conditions in the first place;
2. I find it extremely unlikely that such factory owners would have a dearth of prospective (eager, even) employees.