Aside from price discounts, Disney likely also manipulate blue card minimum. As blue card minimum climbs, people think "this is my last chance! it keeps rising!" and pay up. Eventually the minimum rise to some unsustainable level such as 250 or 300 and no willing buyer is left. Disney then slowly drops it, and those who held firm now think "wow this is as low as it'll go, I better buy now". This is the same kind of psychology that causes people great losses in the stock market, except here Disney actually control all the parameters and all we have is our discipline/willpower.