That's the secret, really. Any market where product can be manufactured in volume is a market that can be targeted by the benefits provided by the Chinese manufacturing machine. Limited volume products are not a good fit for this system.
That said, I don't really understand the surprise or revelation perhaps implied by the author. What is so special about a tablet? In terms of the hardware involved and the manufacturing process, well, nothing. Absolutely nothing. A tablet is no different than any other electronic device.
And, yes, while a stereo amplifier or a CATV tuner use different components, a tablet is subject to exactly the same manufacturing process and obeys the same economic rules. Any product that can be manufactured in the tens of thousands, hundreds of thousands or millions of units per month will, eventually, race for the bottom in terms of pricing. This does not necessarily equate to lower quality.
The question that we should really be asking is: Why are we paying so much for tablets in the US?