The average income per person is $6,600, but still 10% of China's population, mostly rural people, live on less than $1 a day. (There are some very rich people in the cities bringing the mean up) The people working in these factories are mostly rural youth, not well educated, doing the best to provide for their families and earn more than what they can doing small scale farming.
I'm not convinced that how our western eyes view things is the same as how locals view this. Even taking home $.50 an hour like the article says means $2000 a year. If you used to be making a dollar a day, this factory job is much better than a dead end job as a farmer. Just keep that in mind.