I personally think that make the mold is the most important part, so if anything that is the part I would not want to give up control on.
We tent to work with local injection moulding firms that have all the facilities on-site to make modifications to the tools and would check the designs of the tools by the Chinese before they start cutting metal.
There obviously is a risk in going to china that you will have to go out there to solve a problem but we are much happier with that being during the six weeks that they are making the tool and not the 5 years that it is being used.
Here are some tool numbers that I have: US cost = $30k, 8-10 weeks. China cost = $5k, 6 weeks. That is for a tool I quoted last week.
I slightly differ on where to manufacture the parts. Because in my industry pennies matter due to several mark-ups in the chain, we manufacture in China. But as samwillis said, it may not be needed in your business.
samwillis is right when s(he) says that parts and power costs don't change much, but labor does. Labor in the US is $25 / hr burdened, and in China less than $4 / hr. If your parts are labor intensive, it makes sense to be there in China.
What you say echoes my understanding of creating a product 'in China'. Often there are loads of steps where it makes sense to use local talent instead.
This means a lot of the rhetoric of 'jobs going overseas' can be empty.
I think in future that local firms will have a chinese manufacturing partner and list this fact to clients as a 'we save you money this way'. Local expertise with approved baseline manufacturing cost.
Sometimes it just makes sense to be in the US, and we take full advantage of that.
This works well if you are making a product in the thousands but would probably not be the right solution for tens or hundreds of thousands.
China is very cost effective for people time, like making a mould tool, but power and raw materials does not vary as much. A building full of machines making plastic parts has a similar cost wherever it is in the world. I think that as people become more concious of the environmental impact of the products they are buying companies will begin to move to a model where they manufacture the product much closer to the consumer and save on shipping it around the world.