You get the artifact creature master with Urza, Chief Artificer, the gargantuan The Capitoline Triad, who fuels historic synergies and encourages you to play massive artifacts, and then Imskir Iron-Eater keeps your artifacts going with a strong draw effect when it comes into play
Cards such as Accursed Marauder, Fleshbag Marauder, and Merciless Executioner all accomplish this, and have a mana value of three or less, allowing Squall to bring them back and force another mass sacrifice every time it connects for damage
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)
Also, they all enter the battlefield tapped, as most non-basic lands do