That second activated ability makes a solid outlet for an absurd (or even infinite) amount of mana if you have a way to make that happen
Like most Magic: The Gathering cards, the value of Search for Tomorrow 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 (Dominaria United Commander)
For two-mana, you get to bring back a legendary creature from your graveyard to the battlefield, giving it haste for the turn
This is good because an 8 mana commander is kind of steep
In case Korvold can't finish the job with aerial attacks, the deck should either draw or tutor for Revel in Riches as a powerful alternate win condition
Check out our list of the most valuable MTG cards, and our list of the most valuable cards in MTG set, Lorwyn Eclipsed