Like most Magic: The Gathering cards, the value of Mind Flayer 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)
Hitting multiple targets is critical in Commander since one-for-one removal, while necessary, puts you a little behind
Abilities that trigger whenever a player surveils wont trigger
While the clear power creep on Merciless Eviction feels needed and earned bear in mind that its symmetrical, and hard to break symmetry on without taking too many turns off
A single Echoing Courage turns six 1/1 Insects into 18 damage headed straight at your opponent
Ideally, you'll want to start with Snorlax in the Active Spot, even though you won't be able to dish out damage due to the Energy requirements