Injection moulding is used to create many things such as wire spools, packaging, bottle caps, automotive parts and components, pocket combs, some musical instruments (and parts of them), one-piece chairs and small tables, storage containers, mechanical parts (including gears), and most other plastic products available today. Injection moulding is the most common modern method of manufacturing plastic parts; it is ideal for producing high volumes of the same object.
China labor cost is still much lower than US, during past 10 year, China labor is rising every year, it's about 500USD-1000USD/ month, but please don't forget the productivity of individual labor increase as well. Low cost production is still one of the main reasons that China maintains the advantages in injection molding industry.
Quality of made in China have been labeled bad, still, look around you, there are not just low quality made in China, but also some of the best quality product, like Apple iPhone, iPad, all the molds/ injection molding are done in China. What you need to do is keep your eyes open to find a good injection mold supplier. You can't not deny that lower quality products exited in everywhere, even in United States.