The Mountain House Pro Pack are just a "scam" (I really dislike using that word, it gets tossed out so often that it has become meaningless)
The Pro Pack meals a slightly more than half the weight of the regular bags because they contain just a bit more than half the amount of food. They are TRULY a meal for one, a meal that leaves you hungry for more just like actually splitting a traditional "2 serving" meal resulting in two hungry people.
That said they have removed the pretty pointless air pillow effect of their old meals and so have many of the brands, shipping is expensive and most of the expense is based on size rather than weight (dimensional weight is used almost universally these days). When you fill up the trailer of an 18 wheeler you are paying almost the same rate for a load of pillows as you would for a load of bricks, the bricks would be somewhat more expensive because heavy goods burns more diesel but the cost of driving a truck across the country is mostly the cost of drivers and equipment depreciation.
FYI - Alpine Aire and Backpackers Pantry meals contain very little air.