Legendary Angel creatures have always been historically underappreciated by the Magic players. They could be seen as a one or two copies in some sideboards, such as Baneslayer Angel or Shalai, but as soon as they entered the battlefield they would most likely win you the game.
Aurelia is a slightly different case, due to its devotion to two colors instead of one: white and red. This means that it will not work as a sideboard plan, but only as the headliner of an aggressive Boros deck.
As a result Aurelia will be seen only in very small number of decks, so the price will most likely stay where it's at.