Amazon produces 2 versions of the Kindle: 1) sold at amazon.com and targeted at US residents. 2) sold at amazon.co.jp and targeted at Japanese residents.
The Japanese set is cheaper than the US set*, but:
- if there's a problem with the set and the customer needs to get it exchanged, Amazon US honours only US sets**. Japanese sets owners need to communicate with Amazon Japan for technical support, and that would require the customer to be able to speak/write in Japanese.
For this main reason, SGKindleshop only sells US sets, even though they are more expensive.
*The reason is that Amazon wanted to break into the Japanese ebook market, and they have done very well in that regard.
**We have verified this when we tried to help a customer obtain US service for a Japanese set; the serial numbers are all known to Amazon. The Kindle with a faulty battery/motherboard thus became unusable with no recourse to an acceptable solution.