I worked for a big electronics company several years ago. I was responsible for product management of a new PCB and we were told to send our gerbers over to a factory in Asia, not Shenzehn, to have boards built. Prior to this we always used US manufacturing. The first articles came back and were a mess. Blue wires everywhere. Not what we ever saw with low volume builds in the US. We spent two months fixing everything. By the time we were ready for another run, a factory in Shenzhen had already turned out exact duplicates of our working original boards, including our logo silkscreen. After that it was only a matter of days before we saw other factories in Shenzhen on the same block producing our boards. We gave up the project. Not only was our design ripped off, but the factory that stole our design had their copy of our design ripped off.
Suffice to say, everyone will sell one board in Shenzhen. Even multi billion dollar companies get ripped off. This is why you see so many of the same cameras coming from different factories. Is it worth the risk? There may be some advantages in prototype lead time, but if you are going to build there, you better have some way of protecting your IP, if you really care.