To determine the total cost of a spell, start with the mana cost or alternative cost you're paying (such as a flashback cost), add any cost increases (such as kicker costs), then apply any cost reductions (such as that of Emet-Selch of the Third Seat's first ability)
A 13/13 Lizard Horror with trample is likely large enough of a creature to end most games in a couple of swings, even if you happen to be playing Commander
I dont see Heirloom Mirror in many decks because black has more explosive ways to draw cards and stock the graveyard
He clearly wants to end up being a Voltron commander, focused on dealing commander damage to win the game while using tokens as fuel
All of these, along with how many Treasure tokens you can create, make it trivial to reach the 30 artifact threshold you need to win the game with Knuckles' Treasure Hunter effect
Keep that in mind when evaluating two-drops and creatures in general