Where are you getting only $13 from Tenso from? Between the EMS shipping charge, and their own service fee, the cost is usually closer to ~35 dollars in total. While you would still save some money buying from the items from amazon.jp, the saving aren't as great as paying only $13. Now Tenso does often do promotions with Rakuten, which can often time shave off around 3,000 yen from the total shipping cost, that does often lead to significant savings on certain items of over 10,000 yen total.