The fact that they are used 4-of in that deck as well as that they are generally reasonable cards is the reason for the latest rising price.
Not to mention the "buy-out-hype-that-Card!" that comes up so often when a card starts to shine a little bit in modern ;)
This plus basilisks collar makes the card great across all formats and even without it, the fact that it is colorless makes it an easy inclusion in any strategy that needs a pinger.
This just got reprinted in the challenger decks, why does this cost more now then before???