Sleep of the Dead

To determine the total cost of a spell, start with the mana cost or alternative cost you're paying (such as an escape cost), add any cost increases, then apply any cost reductions. The mana value of the spell remains unchanged, no matter what the total cost to cast it was and no matter whether an alternative cost was paid.

Escape's permission doesn't change when you may cast the spell from your graveyard.

If you cast a spell with its escape permission, you can't choose to apply any other alternative costs or to cast it without paying its mana cost. If it has any additional costs, you must pay those.

Sleep of the Dead can target a creature that's already tapped. That creature won't untap during its controller's next untap step.