This is a quick guide for buying a mid level laptop (based on recommendations given to one of my friends recently).
For ultra portable perhaps asus eee pc is a clear leader (for now) http://kakaku.com/item/00200916376/
A very nice site for comparing the prices is http://kakaku.com/sku/pricemenu/winn.htm
Note: sometimes you can get quite a bit better deal by clicking on one of the advertisements on the page.
Cheaper models such as Vostro, and Ispiron do appear to be cheaper in US. However for the higher scale computer such as XPS M1530, Japan has a slightly better prices.
It is cheaper through soho (the XPS M1530)
Also in US it comes with 1.6 Mhz CPU; in Japan 2.0 Mhz (this upgrade costs in US $100)
XPS M1530
* SOHO 104,800円 (943 USD)
CPU 2.0
http://configure.apj.dell.com/dellstore/config.aspx?c=jp&cs=jpdhs1&l=ja&...
Personal 123,930円
http://configure.apj.dell.com/dellstore/config.aspx?c=jp&cs=jpdhs1&l=ja&...
US Personal $1,000
CPU 1.6
http://configure.us.dell.com/dellstore/config.aspx?c=us&cs=19&l=en&oc=DY...
US SOHO $1,000
CPU 1.6
http://www.dell.com/content/products/features.aspx/xpsnb_m1530?c=us&cs=0...