I agree with Pete850's comment about these factories not being sweatshops, I also didn't see any of them - In fact I saw well lit work areas with clean benches.

Pete - PM me If you are likely to come anywhere near to Tianjin when you are next over here, it would be good to catch up with a fellow expatriate modeller. I can introduce you to a couple of the factories that I have found over here (I'm not in the model supply business - I just fly with a couple of the people).