PSO Gamecube has independent servers up and running, including coded events they're just private servers. Private in terms of the fact that it takes a few days after signing up for an account to actually get it. Also if you don't play for a month they delete your account. That's why it's still worth money, also it's hard to find these days.
Ocarina of Time Soundtrack was limited edition. The gold cart OoT is worth quite a bit more as they were only for pre-orders. Don't know if you saw it on EBay.
Panzer Dragoon was very limited print run. One of the harder to find games.
Rez and Ikaruga are two of the rarest games produced. I was so lucky to pick up my GC copy of Ikaruga because I lived in the middle of nowhere KY and the damn thing sat at an FYE for over 2 years before I finally looked the game up.
What you're paying for here isn't a game. It's a collector's item.
Sure you can get all these games on emulator or on XBL or PSN but it's not the same as saying you own an original copy of "X" game.
Like I own an original copy of Final Fantasy still in the box with the manual. It's the only thing I have from my NES that wasn't destroyed. I believe it's worth quite a bit right now.
EDIT:
Yup
http://cgi.ebay.com/BRAND-NEW-FINAL-...item335faf7d3c
And more than likely mine would be worth around 2/3 of this.