Current demand is low because there hasn't been a compelling use for Move for years. The prices reflect that demand. The only reason sellers can afford to price it so low is because these people working out of their garages got a bunch of units super-cheap back when major retailers were getting rid of them years ago.
That being said, anyone who buys now in fear that prices will skyrocket is only going to save themselves maybe $30-50 total. Retail is only $20 more per Move, and don't forget the likelihood that Sony's 2 Move bundle (w/ or w/out camera) alongside PSVR's launch will offer a very good value.