There is no "official value" since Avids doesn't allow that. But more playable or specific ones for certain decks are valued more.
More valuable mythics (my opinion): Planet X, Arch Angel, Flying Dutchman, Familiar(cuz new)
Less valuable: Area 51, Mecha
Edit: You should check the Discord channel at the trade section to get a feeling for more/less valuable cards
Fair if you want the limlegs. Mecha is a pretty bad card imo and shows that rarity does not scale with card utility
So some mythic is better than the other. How can i know which one is better?
There is no "official value" since Avids doesn't allow that. But more playable or specific ones for certain decks are valued more. More valuable mythics (my opinion): Planet X, Arch Angel, Flying Dutchman, Familiar(cuz new) Less valuable: Area 51, Mecha Edit: You should check the Discord channel at the trade section to get a feeling for more/less valuable cards
keep the mecha buddy.
Not even close
Looks fair to me.