I consider each cards novelty, flexibility, and play patterns to determine which are worth building and which are value-slop
We don't want blue-red decks to have access to an extra card in every game of Commander for all time (and it's not like it's a color combination that needs the help!) nor have players who don't have access to Lutri get told they "have to" play Lutri
Even if you can't have Gilgamesh, Master-at-Arms do all the work, you can deal massive combat damage with other creatures
Wizards is not afraid to poke fun at itself (at least over its less controversial slip-ups) with these cards, either
Without that, almost regardless of age, the lowest priced sets tend to hover below $100, like Fallen Empires , Fate Reforged , and Dragons Maze
If its a permenant card, you may put it onto the battlefield