Just checked out the yahoo.com.tw auction site, I noticed quite a few 400s ranging from between 55,000-80,000NT. These must all be illegal (ie unlicenced, and unable to get licenced) bikes, right? Just curious…there are some very nice looking cb400s there, and some of them seem to have the yellow plates (fake?), but surely you couldn’t get one legally for that kind of price? If only… 
at that price range… they are definitely illegal… ranging from just plain stolen from Japan to imported as “parts” without paying tax… in either case, you cannot get a plate for them… unlicensed bikes were once the norm, but now those over sized yellow numbers are now very much de-rigueur…
Since there’s a big beginners market, clean, licenced CB400’s are snapped up quick, but there are quite a lot of them about though, so don’t give up…