There's an obvious and simple reason why
This is just Monopoly with extra steps I think
A 10, or Gem-Mint 10 as some companies call it, is pristine: no scratches, perfectly centered, exactly how it came off the press
Because every single unit becomes a legitimate threat to the opposing Leader's life total, defenders are forced to make uncomfortable card trades early in the match
One of the biggest reasons this card ranks highly is that you have a easily triggered card draw that costs you no mana, so a free sacrifice outlet like Phyrexian Altar does incredible work with your creatures: drawing and paying for spells with very little assistance
While Tyranitar has fallen off significantly after touching the $30 plateau, it secures its place on this list, but it may be in jeopardy if this card's value falls into the $23 range