Cascade doesn't apply a cost reduction, it provides an Alternate Casting Cost (of no mana). Additional costs (such as "sacrifice a creature") MUST be paid, and optional additional costs (like kicker or multikicker) CAN be paid, but have no "cost reduction" applied.
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Hence the flavor text! Woop woop.
The flavor text that I LOVE, by the way. This card is neat.
@damagecase: White, by virtue of the color pie, gets better removal than green. Also, Path to Exile is undercosted.