the card itself and the set it comes from also need to be worth collecting, but if the stars align, a numbered card can be worth a life-changing amount of money
This isnt an entirely unexpected choice as the prevalence of Ash Blossom makes Pendulum Call an extremely dangerous card to use in the current meta and furthermore conflicts with the decks focus on destroying its own cards
Also the fact that they are all EARTH monsters are useful since "Grandsoil the Elemental Lord" or "Gigantes" can fit in to support them further
cards, the value of Ryu Kokki depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Gold Series: Haunted Mine)
This is consistent whether the boxes are newer than Aetherdrift with 30-packs each and with the 36-pack draft booster boxes that stores may still have on display
That means they are worth something