Effects that increase or reduce the cost to cast a Trap will apply to whichever cost you chose to pay.

You may ignore a Trap's alternative cost condition and simply cast it for its normal mana cost. This is true even if its alternative cost condition has been met.

Casting a Trap by paying its alternative cost doesn't change its mana cost or mana value. The only difference is the cost you actually pay.

The player you target with Runeflare Trap doesn't have to be the opponent that drew three or more cards this turn.