The short answer....skip eBay and select a proxy bidding service....then search on YJA.....
Here is a list of recent completed auctions for Bandai VF-25's....look at the ending prices for the renewals to get an idea of what they will cost you...if you are patient you should be able to pick most up for less than 20k JPY plus proxy and shipping fees.....
http://closedsearch.auctions.yahoo.co.jp/closedsearch?p=VF-25+DX&aq=-1&oq=&x=33&y=46&ei=UTF-8&slider=0&auccat=0