It's now cheaper to ship items from Amazon Japan. They have reduced the hefty per-shipment cost. For exact numbers, check here: http://www.amazon.co.jp/gp/help/customer/display.html?nodeId=201213350&t...
Per shipment to Singapore dropped from 1900 yen to 600 yen. Per-item increased by 100 yen to 400 yen per item.
If I remember correctly, per shipment to USA used to be either 2600 or 1900 yen. It's now 800 yen. Per-item increased by 100 yen to 400 yen per item.
In general, per shipment is now around 1000 yen. A very significant reduction from previous shipping charges.