Koraidon [Holo] #124 (Pokemon Scarlet & Violet | Pokemon Cards) prices are based on the historic sales
Basically, for a flashback card to be playable, the front half either has to be close to on-par for its effect, so the flashback aspect of the card is a bonus / afterthought, or the reward for getting the card in the graveyard is good enough that you don't mind building around a card that's not that great in your hand
They were made to support the magecraft mechanic, so cards with magecraft and prowess are a good fit
Chaos: Whenever you roll Chaos, draw seven cards
Its ideal for a spider typal deck with Ishkanah, Grafwidow or Spider Spawning that turns every creature into a lethal threat
With 4000 attack by default, thats definitely not the kind of damage they could survive easily