my friend brought his teen titans base set over the other day and claimed he couldn't see anything in the instructions regarding if you still need to pay the cost for time travel cards after you have bought and then played them yourself?
Technically all Time Travel cards are from Crossover 3 and have nothing to do with Teen Titans, but anyway...
From the rule card:
"You may discard a card from your hand to play this card from the Line-Up or Super-Villain stack..."
The important part is underlined. The 'discard to play' only applies if they are in the Line-Up or are the current Super-Villain.
An additional bonus question although it may be in the wrong section but is there any other expansions that focus around destroying cards for VP or cards that have effects when they are destroyed other than forever evil, crisis 3 and the watchmen expansion?
Mostly just Forever Evil and Crisis 3, what with them being the "bad guy" sets.
Watchmen -can- destroy a lot of cards, but there isn't really much for 'bonus' attached.