The base stats are 85.3% gold efficient, without its passive.
The passive is worth at least 205.56g, using the least favourable combination at the most minimalistic level (Anivia at Lv 3) for cost efficiency and the 1% max HP scaling. For it to be efficient with the passive, a champion must have a minimum 1020 max health, meaning that by Lv 11 this item will always be cost-efficient.
The living armor protected the greatest troll warrior in the entire realm during the bloodiest and most devastating battles of the Rune Wars. Deep within the dark woods of Crystone the living armor waits to protect its next owner. A word of warning required before seeking out Warmog... it will protect you for a time, but when it grows tired of you, who will protect you from it?
Passive changed to: Permanently gain 4.5 health and 0.15 health regeneration per 5 seconds per minion kill. Champion kills and assists grant 45 health and 1.5 health regeneration per 5 seconds. Bonuses cap at +450 health, and +15 health Regen per 5.