$100 for a sealed common game is ludicrous. What's stopping people from repacking a used copy with shrink wrap?
I have worried about this for a long time, actually. I wouldn't pay $100, but if it looked in reasonably good condition anyway, I would maybe buy it around $40. I used to own Dungeon Explorer, it's one of the games that really made me embarrassed of the TG-16 cover art. Of course now it has it's nostalgic charms but as a kid...
Worse yet though on a related note, I'm worried about people making Bootleg NES, SNES, Genesis, etc. cartridges, with say like a flash rom on the inside holding the game. Again, I won't spend a lot on most games so its probably not an issue, but I do wonder who is getting ripped off out there. I guess that would be damn hard to do with a TG-16 / PCE hu-card, since you can't swap out the innards so easily.