Considering the myriad options you have for returning cards from your graveyard to play, you should treat this Golgari sorcery as just plain better than Shared Summons, even if creatures in your graveyard are a little more vulnerable than the ones in your hand
But scarcity alone cannot explain the full market
Consider the Power 9 First up in any valuation and list building for MTG, you're going to have to make a call on how you handle the "Power 9"
Maulfist Doorbuster: [Category 2] ETB yield is 2 Energy for 4 mana, then you can spend 1 Energy to cause a creature not to block
This allows collectors to choose which specific cards they want and can lead to higher prices overall
They could have done plenty of things differently to actually make these a massive success and warrant a mase print run but instead they made them generic reprints that just have a stamp on them #6 Golly, can't wait for all the middle-aged white guys to buy these up and immediately invalidate the inherent purpose of these packs