"Cost enters into the equation in other, less visible ways, too. For example, some figures are highly valued but no one needs very many of them. When individually packed, these rare figures are much more expensive to manufacture in limited quantities than the common figures. That additional cost has to be passed on to the customer, either by increasing figure prices across the board (nobody wants that) or by charging more (in some cases, a lot more) for those special figures, which in turn cuts down demand even more. By making those figures rare and packing them randomly, they become no more expensive to produce or buy than anything else in the set. It's easy to assume that Wizards wants everyone to buy 20 packs of figures just to get one mind flayer. While we certainly hope everyone will buy 20 packs (and once you see the figures, we think everyone will want 20 packs), if a mind flayer is the only thing you're after -- well, that's what trading is for."
So basically... I save money by buying miniatures I don't want?
Look, not many people are going to want a Krenshar (or whatever that face-removing abortion of a monster idea was called). There's no way that Wizards is going to convince me that them making 20 Krenshars for every 1 person that wants one, while everyone scrambles for the miniatures they want, is a good thing.