You'll see the really low prices a few hours before the actual performance. Apart from that you can refer to my prices in the original post, when it comes to resellers. Auction prices is a bit different, check
http://auctions.yahoo.co.jp/ for them, just do a search for Arena Tour 2006.
The reseller store tickets range from around 7000-75000 yen each depending on seats and how long it's left for the performance.