Catalyst the Protector is 94.4% gold efficient without the passive.
The passive regenerates 150 health and 200 mana, which is the equivalent of a health potion and two mana potions (total value of 105g). The passive provides 105g*(level-ups since purchase), for a maximum value of 1890g. This increases the gold efficiency to (1133 + 105*lvls)/1200, with a max of 251.9% gold efficiency.
Catalyst the Protector is gold efficient after the passive procs once.
With the increased durability and sustainability it provides, Catalyst the Protector allows champions to remain in their lanes longer without needing to recall.
Champions at higher levels require more experience to level up, making this item less effective at providing sustainability at later stages of the game.
The word Catalyst means something or someone that precipitates or causes an event to happen without being used up itself, possibly referring to the passive effect that causes massive regeneration whenever a champion gains a level.