A Rare Mickey Mouse or Elsa card can command higher prices simply because fans love these characters
She's solid, she has a higher ceiling but a lower floor than her old version
The power and toughness comparison that determines if a +1/+1 counter gets placed happens when the trigger resolves, so a well-timed pump-or-shrink spell can stop that from happening
Through the Breachs spread of 39% is not as low as that of Goryos Vengeance, probably due to its larger supply, but as with Goryos Vengeance, I am confident that Through the Breach is undervalued right now, more so for the fact that Through the Breach is ran in other archetypes beyond Goryo Reanimator
But, like the changes between this ghost-type and its Mega evolution form, this card is subtly effective
I keep around 15% of my bulk box pulls for playing in various MTG formats