Cry Havoc states that you can remove one normal monster from play from the graveyard to normal summon 1 normal monster from your hand during your main phase. Why could I not remove Neo the Magic Swordsman from play (he was in graveyard) to summon Blue-Eyes?
Because Blue Eyes is 8 leveled monster. It means 2 tributes must be needed for another summon.
Normal summoning a tribute monster will still require tributes.