Hmm, it seems this sudden jump has happened in a week's time to boot. Might be like the antique radio market two years ago. Prices spiked, then the market crashed and burned. Console radios bringing 200-300 dollars at auction places here in March were only bringing 20-dollars by November.
Give up on the II, those command $1000 and up easy. And have been doing so for at least the past 3 or 4 years. Other than as an historical artifact, value to a collectard, the standard II is a POS. II+ and //e are infinitely more usable and convenient.