The common perception of Chinese made goods is that they are inherently of poor quality.
This is so only because the purchaser makes specifications to which the Chinese manufacture the item.
If the order is to make an action of particular design and composition to a price point, the Chinese will do just that. If the same design is specified but with higher quality materials or specs, to a higher price of course, they will make that too.

I agree that these Sarco actions are very attractive as to cost, but makes one ponder... just what is the trade off?

Unless you MUST have a magnum length action (and lets face it, who really does?) I don't know why you wouldn't just buy a 1909 Argentine and build on that.
Similarly, if you are having a big buck custom Mauser built by one of the big name guys, why not just source an original commercial Mauser action? May be a few hundred dollars more on the front end, but on a $10-20K rifle, isn't it worth it?