In Ikariam, Ambrosia is the premium currency that allows faster building, expanded population limits, additional simultaneous construction queues... advantages that a free-to-play player cannot match without investing extra time or money.
In 5Dim, time boosters (construction, production, research) also exist — but they are obtained for free by completing missions and achievements, or by buying them from other players in the player market. No booster modifies combat stats, so the battlefield is always fair.