Is there a list somewhere with the low/high/average prices that VB games sell for currently? Something possibly incorporating the condition the game is in and what accessories are included? I see the MSRP is listed on the games on this site but I can’t find any “used” pricing info. Obviously some games are rarer than others, but the prices seem to vary wildly on eBay, because the people creating the auctions don’t seem to have a very good idea what the game should be worth. Example, I’ve been watching for a copy of 3D Tetris and I have seen several “Buy It Now” auctions for more than $100 USD, and I’ve also seen some used cartridges in the same condition sell for <50 USD.
As a side note, I think it's kind of shady that quite a few people try to sell "3D Tetris" and then explain in the fine print of the sale that the game is actually "V-Tetris" from Japan. They are two completely different games and it's very misleading.
I go with the rarity scale. When I actively extended my collection (got all US games now, don’t really want the japanese games that much…) I would check all new virtual boy related ebay auctions once a day, that gave me a good knowledge of what something is worth.