First, a card suddenly becomes more popular, and lots and lots of players start picking up a copy or playset (perhaps combined with some number of "speculators" who buy cards in the hopes of making a profit), and (especially if it's an older card without a lot of supply to begin with) the end result is that all or most of the copies of the card are purchased from various Internet vendors and sites
Also, its a creature we can reanimate later, so thats always a huge plus
Still, theres plenty to celebrate about them when we finally do get them, not least the decision to have parity across the card designs in both Japan and internationally, including the far superior (and I will fight you) gray borders, that much better let each cards art shine
Each mission has its own locations, victory conditions, and even special rules
The really high prices paid by top level collectors are only for PSA 10 cards, and a PSA 10 is very often worth more than twice as much as the exact same card at PSA grade 8 or 9