I have enjoyed reading this thread.
In the last 5 years since having the internet at home, I have bought maybe 50 titles that were regarded as rare. After much thought about it, only about 10% of them were worth a shit. But it didn't matter because the titles in question were still worth what I paid. Who cares what something is worth or what you paid if you can retrieve the purchase cost?
I bought a sealed DDP on the Saturn and before it even arrived someone offered me $80, Gun Frontier and another title for it.

. I just spent $45 on a opened copy a week later
Some titles like Adventures of little ralph gather alot of attention because its a saturn killer

. Yeah, i'm gonna spend $100+ for a title because it has better 2D graphics than the saturn? I don't care if it has better graphics than the Saturn. What I care about is if the game is worth experiencing or not. Especially for $100+.
Pacrappa made a good point in another thread that Neo Geo fans dismiss Spinmaster, Zupapa and such in favour of stuff like Magician lord. Which I agree is crazy.
Obviously some people are buying to have what most people would like to have, others are just buying to own and play a great game.
One thing I have learned is that having a rare game is a risky business. If that title ever gets reported to another system you will lose alot of what you got invested in it.
This industry has become 2 dimensional as it transcended into a 3D world.