Stop looking at Amazon. Those prices are way inflated. Mega Man Legends 2 completed listings are about $40-$60 complete on eBay. That's not really that much. Certainly not when you can legitimately spend $250 to $300 for Panzer Dragoon Saga or $150 on Radiant Silvergun or $200 on Misadventures of Tron Bonne.
I understand that might seem like a lot to someone who doesn't own anything rarer, but it's really not unreachable. It's one full priced modern game.
As for me... I've found out a few things I have are more valuable than I knew... M.U.S.H.A. for Genesis, the aforementioned Tron Bonne... so this thread has been helpful that way. I have lots of stuff that has held it's value or is worth more than I paid originally, which is nice. Some highlights...
Cosmic Smash (Dreamcast)
Ikaruga (Dreamcast)
Napple Tale (Dreamcast)
Bunch of other Dreamcast games.
Large assortment of SEGA Saturn games.
Some Genesis games.
Pretty much all my Neo Geo AES collection.
The stuff that's really interesting to me is the curiousities that I've found along the way that you simply don't see available on eBay often. For example, I have Freespace 2 for PC... on DVD. It was a Euro release. It's one disc. I have maybe seen it listed once on eBay. It's a truly rare item. Of course, you can buy and download the game for $5.99 from GOG.com, but this thing is unique. Maybe not worth much? I don't know.
I also have a conversion of Neo Turf Masters for AES on the Neo Geo. Conversions rarely fetch a lot because no one really knows the value of something like that, however this one is a conversion of a game that's print run was so low on AES that it's definitely "valuable". Is it worth $300? $3000? I don't really know. It's fun to play it, though.