You reckon the perfect information version is cheaper than an algorithm that works only on the tiles near to the unit? But this quickly gets too complicated to discuss; there's the confusing matter of precalculation versus live updating.
The perfect information version calculates the path once on click, the local version needs to recalculate every time the unit moves (and new tiles are "seen")
The perfect information version calculates the path once on click, the local version needs to recalculate every time the unit moves (and new tiles are "seen")