What!?! That cartridge cleaner thingy was actually valuable!!! I had one a long time ago but I broke it a long time ago and trashed it. My god, i'm filled with so much regret right now. Velfarre you better not be shitting me about that.

I get the whole thing with that this guy is a collector and yes that games could and are something that people collect and would be desirable to do so.  I am not trying to see either that things have to have a practical purpose to be collected either.   I do think though for something to become a collectors item in the first place it has to be something that was originally desirable, and I don't see how this was originally desirable in the first place considering that well who wants a dumb ol' demo?

i remember back in 1997 a prototype english cartridge of mother for nes surfaced and sold, but that didn't go for near as much as this did. the guy who bought the cart paid about $125 and rom hackers paid $400 for the opportunity to backup the data. i have difficulty imagining how any nes game could possibly go for more than what mother is worth, although i could realistically see someone paying in the 10k range for the prototype mother cart.

a cartridge specially produced for use in a Nintendo-sponsored gaming contest

Chrono Trigger in the original package goes for over 1k, so does Earthbound. I can't really understand Chrono Trigger, as it's not exactly rare, but Earthbound I can; it was discontinued I think very early after being released because it wasnt LOL JRPG and that was all that was popular at its time of release (same time as Chrono Trigger, FF4, etc.) <- Needless to say it failed. People still pay around 400$ for romhacked carts of EB0 because they don't do research ahead of time. Basically, people do some fancy soldering work and put an EB0 rom onto a random cart. Most of the time it just displays the piracy notice. The piracy notice in EB doesn't exist, it just increases the monster spawn rate to 100% and deletes your save file right before Giygas; sneaky! [/verbose post]
 EDIT: The article you posted was the article I was going to post hurray!

 As for this, I have a bit of a tale. IIRC, the fansite starmen.net was going fucking mad over what they thought was a leak of the n64 M3, but I think it turned out to be some shitty tennis game once or something once the original leaker got around to hacking them so he could open em'. They came in these cute little blue blocks and had masking tape on them.

Speaking of Snes carts, I was surprised at how available they are in Japan, especially in Akihabara. When I went there were atleast 3-4 shops dedicated to Snes/Nes and I was able to buy FFV and FFVI for 1000 yen each (in jap ofcourse).