Well, in my experience, unless youre going hard on enabling your catch-up ramp (which Ill cover later in the article), it starts to drop off in value as soon as you go above two mana
Witherbloom, the Balancer Affinity for creatures first showed up on a simple 4/4 with vigilance and that Argivian Phalanx costs two less mana than Witherbloom, the Balancer which is a stronger creature and grants a huge cost reduction and will straight up give you nearly free colorless instants and sorceries like Warping Wail or Skittering Invasion
All cards are part of a complete commander deck and can be mixed with regular mtg cards if you want to change it
The most valuable card (non-foil, non-alternate frame/art) thus far is Ugin's Labyrinth
Its for that second part, though, why many people will find room for Wondrous Crucible
What usually happens in a multiplayer Commander game is that everyone will start-off paying the cost, but when one person breaks, they all will, and then youll be buried under your own cards