Perhaps players thought it would be a shoe-in for the Eldrazi precon, or else the main set, so were holding off in case the price dipped
It only produces green, but it produces mana based on power, so it will eventually produce 4-5 mana, which helps with X-spell utility
Like most Magic: The Gathering cards, the value of Ardyn, the Usurper depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Final Fantasy)
So how can you and I, the cost-conscious, frugal-minded, I have a life outside of buying and selling Pokemon cards community, get our hands on sealed products and still collect our favorite cards from every set