Upon closer inspection, they only use 1750 construction workers for 4 years per reactor. By your figures, that's 0.7 billion total. Let's assume the Chinese pay absolutely nothing for nuclear-reactor-qualified workers. Where do the other 4.3 billion per reactor go?
The actual construction cost I recall being cited for this project is closer to $9.5 billion. The remaining $4.5 billion are the interest you have to pay on a somewhat-high-risk $9 billion loan. Oh, and you have to start paying interest when you borrow the money, but don't start having revenues until 4+ years later.
Cost of capital is very different in China, depending on who's funding the project and how. It's hard to compare exactly what the construction cost component of the Chinese numbers is, or whether they're even including the cost of capital at all. I strongly suspect it's not, since the article quoted is talking about the revenue Westinghouse/Shaw will receive, not the expenditures of the purchaser.
So we're really comparing about $4.75 billion in the US to $2 billion in China. If the actual structures are somewhat different, land in the US somewhat more expensive, a lot less in the way of earthmoving needs to be done in one of the locations (say because people aren't worried about environmental impacts), then I can see a 2x difference in the price tag...
