Price elasticity of demand. The EX costs the same as the regular. More product for the dollar. Higher perceived value. Higher demand. Regardless of how much the public wants the extras, people who want it will buy sooner.
Generally, the higher the price, the lower demand goes so supply has to meet demand at an optimal point. Exclusive production pushes the demand and supply curve right (if you were looking at the price equilibrium graph) meaning they can charge more initially (technique is called market skimming) and after sell for less in the aftermarket.
In other words, we're all suckers for paying more for squiggly eyes. What we pay now, covers the cost of discounts passed on to buyers later. The price of Superman isn't 399. It's probably and average of 250-300 once all is said and done and wholesalers buy through 75% of them at a discounted margin. SS relies on us being impatient and buying in to the EX product at higher costs. They save discounts, hold margins tighter, make gross on freight/handling, grab NRDs which can be used to fund production, and set quantity parameters based on initial take. They even get free market research and feedback from psychos like us that post in these forums.
It's a solid strategy.
Then it would really piss you off if you knew how much you overpaid for food