This whole conversation raises two interesting questions, who are these grey importers and why are their prices so low?
The answer to the first is that they seem to be based in Hong Kong or other far eastern locations, where they can keep identities hidden.
The answer to the second is more complicated. Some are simply smuggling and relying on the numbers game to get away with it most of the time. Others seem to take advantage of legal, if infuriating, loopholes in the collection of taxes and duties. All appear to use the pricing differentials between countries, set by the manufacturers, to re-export to their target markets.
America is often the cheapest place for a grey marketeer to purchase stock. The huge size of the market allows the importers to force eye watering discounts on the manufacturers, which the grey marketeers then take advantage of. There will be other countries where this same trick can be played.
There's obviously a lot more detail to be ferreted out but this is as far as I've got so far.