Thats why you should evolve it from the Damage Change Mewtwo-EX
That comes out to 2.5 mana per card, without accounting for the mana you spent on the sacrificed creature, which is pretty decent in the grand scheme of things
The main reason they are banned is that they are very powerful and can create a huge gap between you and your opponent
These transforming double-faced tokens can transform just like the permanents they copy
Going by MTG Goldfish's price tracker, the spike began a week after Bloomburrow released, and it shows no signs of slowing down just yet
Its easy to imagine a control deck that wants to cast a draw spell and a removal spell and get a blocker, or just an aggressive deck casting this card, some other cheap spell, now you have a 2/2 trample haste coming in