How does the Efficiency formula (1000/(1000+E)) work in Dragonfire?

Efficiency (E) reduces both the time AND the cost of actions (construction, research, recruitment) through the game's formula:

`New cost = (1000 / (1000 + E)) × Original cost`

Key points:

• +1,000 E ≈ −50% cost/time (1000/2000 = 0.5).
• +2,000 E ≈ −66% (1000/3000 ≈ 0.33).
• It's diminishing: the first points of E are worth a lot, the later ones less and less.
• E stacks from several sources (research, buildings, buffs).

➡️ The practical consequence: stacking Efficiency early speeds up everything else (Tier 10, recruiting your waves). But don't over-invest beyond roughly 1,000-2,000 E on one axis — past that, returns drop sharply.