Understanding rarity and production is a huge step, but it's just one piece of the puzzle
Having many, many ways to recur the only four extra turn spells available means that the deck has more effective copies of those cards, as a card like RegrowthRegrowth is just a Final FortuneFinal Fortune for two more mana with the latter in the graveyard
Ungraded & graded values for all MTG CN2 Magic Cards
Given enough time for Wizards of the Coast to figure that out, it might be okay eventually to redo
Like most Magic: The Gathering cards, the value of The Deck of Many Things 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 (Adventures in the Forgotten Realms)
Legendary Instants and Sorceries Isildur's Fateful Strike Jaya's Immolating Inferno Kamahl's Druidic Vow Karn's Temporal Sundering Primevals' Glorious Rebirth Urza's Ruinous Blast Yawgmoth's Vile Offering Since were lumping cards together lets talk about legendary instants and sorceries