I'm not buying the Engineering/Component Cost for the Difference.
The Low Power Sandy Bridge has a TDP (17w) that is 8w higher, which should not be immensely difficult to account for in cooling.
If we were talking about the Alienware 11" which includes a Dedicated Nvidia 540M whith a TDP of 35w, then it may be an issue. However, 17w of power should not be difficult to cool. And certainly not more expensive than the cost of the larger LCD, Larger Battery and other materials to make a larger laptop.
Intel likely overcharges for the chip, though it is not any different than the standard chips beyond having lower default GPU/CPU speeds which allow for lower voltage. Heck, Intel could even use Failed Chips that could not operate at normal speeds to fill their quota.
Economies of Scale and limited market competition in this small market segment are likely the bigger issues.