Good grief, there are as many Realforce boards on yahoo japan as there are Logitechs in North America/Euro eBay sites. Too bad I'm not a L-user... I like straight, Model M style enter keys.
Not really if you did not notice the vast majority of those boards are being offered by Japanese shops at new prices not end users selling used products. There are currently only a hand full of actual used ones from individuals and most of the time you don't see that many of them. I will admit that in the last few weeks though the NEO Counter strike which I have never seen on Yahoo Japan and if you search old auctions never before on Yahoo Japan has all of a sudden shown up. Why because the first one that showed up sold for almost $700 USD so those that had them pulled them out of the closet and decided to sell them and at that price I would be tempted as well. You really don't see older Topre boards up for auction very often. The ones you used for examples are some of the few that are actually used boards except for the Just one.
All 45G Realforce 91U
Nope this is a standard variable force 91U not a uniform 45g board if I remember correctly that is. Just is a Japanese shop that had there logo stuck on the board not really a OEM board because the Realforce name is still on it. This is just old stock that a shop is trying to get rid of and not really at much of a discount either.
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Realforce ND01N0 Counter-Strike NEO
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Realforce 108UH SA0100
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The NEO is from an individual the 108 is from a resaler (used computer shop).
Just like the US the vast majority of the boards on Yahoo Japan are junk rubber domes do a search using "キーボード" to find most of the keyboards. It will take you all day to go through the result from that one and most of them will be junk rubber domes.