‘’’’Banishes from Extra Deck for Cost’’’’ is an activation cost that is unique exclusively to “Pot of Extravagance” and "Eater of Millions", the only cards in the game with such a cost.
"Pot of Extravagance" has the unique cost because it attempts to combine the effects of the long Forbidden card “Pot of Greed” and “Pot of Riches”, a draw card that supports Pendulum Monsters and as a result, has interactions with the Extra Deck by shuffling face-up Pendulum Monsters from the Extra Deck back into the Deck.