Just go to Akihabara, there is a web site, sort of like pricewatch, that let's you find the cheapest place to buy electronics in Akihabara or walk just walk around.
I was in Tokyo a few weeks ago, and I bought 2 C3100 for friends, found them for Y575500, which is something like $500, from a place caled PC Select on the 2nd floor or some building. The C1000 was something like $300.
Remember it's 5% higher with a credit card order.
Oh, here's their web site
http://pcselect.co.jp/P.S. I just checked, it's Y33200 for C1000 right now, which according to Google is $283.