While the sheer quantity of potential commanders available has made sure that the format is diverse, the quality of designs among legendary creatures (and eligible planeswalkers) has been important to keep things interesting for players seeking new deck ideas
This turns them into potential 6/6s, which is pretty nutty
So, while $150 for an experience is vastly less than one would pay if playing real competitive Magic, its still quite a lot compared to a random board game, where $150 is going to get you a massive box of plastic figures for some 6-hour epic space game, plus a new deck-building game, plus some old Silverline game from FFG
Duskmantle, House of Shadow and Nephalia Drownyard each tap for colorless mana but have activated abilities to mill a few cards
The cards packs the power you'd expect from two Legendary Pokmon
It fits a need in casual Magic and will be warmly embraced alongside of cards like Stonehewer Giant or Puresteel Paladin