Shipping costs especially overseas are usually really expensive and a nightmare if an issue arises through something like a Yahoo auction. Japanese retailers like Upgarage and Black Hawk Japan, should be okay. I've bought from Black Hawk Japan without issue. Upgarage does have a US location now that sells and ships throughout the US, but I'm sure you won't get the same price break due to the exchange rate as buying through them in Japan. I've seen people with good experiences ordering through them.
You can always check dealers like Fitment Industries or Evasive Motorsports, sometimes they have sales. I would also check if you have any local shops or dealers that are able to source the wheels you're looking for, sometimes they'll be able to get it for you and sell it to you at a discount.