My guess is because it's a fixed blade with one piece of steel, two scales and three screws. The retailer probably committed to a specific order so they were paid for as soon as they were made. Not every offshore product falls into this category or situation. With so many made in the U.S. models and variations to choose from I just don't see what the problem is with a few models being made overseas?
I personally don't have a problem with overseas production per se, but if I'm buying a Buck knife in 420hc, I would like the Bos heat treat. Other 420 just hasn't seemed as good to me. I was under the impression that the China models did not get that treatment. So it is not that they are made in China, it is that the quality is maybe not as good, and for roughly the same price I'll take a Maverick made in the USA over the Chinese 877. And if a US 877 isn't available I'll spring for a Paklite, also about the same price. If it came to light that Buck's chinese knife steel was identical to that of their American made knives in composition and heat treat I would happily buy a Chinese knife. But if I am paying retail on a Buck knife, or if there is a rough equivalent of a Chinese model that is made in the US, like say a 371 vs a 301, then I will stick with the US version.
I think in the case of some Buck knives tradition has a little to do with it too. I would be more likely to buy a less traditional design from China, but if I'm buying a 301, it's gonna be a 301 from the US. Buying a 371 would be like buying an Opinel made in Taiwan, or a Mora from Brazil.