This effect can be done at instant speed , so you can invest a lot of mana in it during the end step before you start your turn, once you no longer need mana up for potential interaction
Wrenn and Six put in a lot of work picking off their earlier creatures, while Ephemerate makes it difficult for those decks to remove your threats
This doesn't seem wholly sufficient to explain the spike, otherwise why didn't it pop off during Bloomburrow, which brought in a popular new bird commander Kastral, the Windcrested
And then, yes, theres that Mega Gardevoir ex, with a degree of intricacy not seen since Akira Egawas Giratina VSTAR in Crown Zenith
Im not going to judge the practice of weighing but instead comment on it to help my readers understand why blister packs tend to sell for a premium compared to booster packs