Like most Magic: The Gathering cards, the value of Pools of Becoming 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 (Planechase Planes)
However, Japanese booster boxes guarantee at least 1 Secret Rare card something that is welcomed among collectors as you know you are at least getting something decent for your cash, while English Pokmon Booster boxes DO NOT guarantee anything
Does your EDH or other deck need a faster way to cast your biggest cards
To bring it back up again, the One-of-One Ring is another extreme example of this since its a one-of-one card
Another thing to consider if playing a build with a heavier white component is the card Resurrection which is a 4 mana reanimation spell with basically no drawbacks
I know you dont believe your opponent