I don't see anything out of the ordinary with those game charts.
-Wild Guns
-Hagane
-Knights Of The Round
-King Of The Dragons
-FirePower 2000
It looks to me like a big spender caused a spike in the prices and they seem to come down just as fast.
Haven't one or two of those games been slated on Game Sack etc (FirePower 2000 sticks out)
so they're not all 'top quality' games.
Someone wasn't sucking up the cream of snes games, just the CIB copies, which always command a premium whatever the format and this naturally dragged up the unboxed versions as well.