Either (A) they picked a stronger card in the Abzan colors (perhaps possible for the player who opened the pack if there was a bomb rare) or (B) they aren't drafting Abzan (more accurate is to say that they weren't drafting Abzan at the time they made the pick)
The new 'More Than Meets the Eye' keyword lets you cast the cards in either form, and you can also convert them during the game
It's not just the card itself that people are paying for, though
Nostalgia, popularity, and the visually alluring nature of these beauties make them the ultimate collectors dream
The Phantom Knights of Mist Claws The Phantom Knights of Break Sword The Phantom Knights of Rusty Bardiche Link 3 DARK Warrior Link Effect Monster ATK 2100 Links: Bottom Left, Bottom Right, Right Materials: 2+ DARK Monsters During your Main Phase: You can send 1 The Phantom Knights monster from your Deck to the GY, then Set 1 Phantom Knights Spell/Trap directly from your Deck to your Spell & Trap Zone
Nor does its popularity outshine those Pokemon