yeah, it works similarly to ebay, stores are set up, and just sell through rakuten.
at least that's my understanding.
It's also similar to Amazon, in the same sense.
Rakuten itself doesn't sell you stuff - they just keep track on your points and account information. There are a number of different stores which focus on different things like, clothing, music & movies, gaming & anime/manga and so on so forth.
You CAN find things for very cheap, but keep in mind that these deals might very well get nullified by the shipping costs. I've only done business with a store called Suruagaya and while they ship international, they use EMS and you won't know the final sum (including shipping) until they've calculated everything out and sent you a mail asking for your purchase confirmation.
So, using the
EMS price chart and keeping en eye on how much a number of CDs/jewelcases and so on weighs will help in understanding what the shipping costs will be like. Of course, once you start adding books & posters etc it becomes rather impossible. Packaging also weighs a bit and you don't know how much bubblewrap they will use (everything has been very well packaged though). I've taken notes a few times when doing business with them and depending on what I bought the packaging weighed from 400g - 1000g. The last one was a shipment of 8 LDs so they packaged that shit pretty tight.
From my notes (which might not be totally correct) 1 CD in it's case (music or game) is about 120-130g while 1 LD can range from 360g to 515g depending on what exactly is in there. Insert sheets, bonus material and so on.
Still, I've found some really cool thing there. Game systems tend to be expensive but some games, books, posters, music and laserdiscs can be had for a steal.