Originally Posted by Shino'sDad
Costs can be replaced always. As long as you paid the cost, it doesn't matter where those cards end up. So if the cost of a card is "Discard a card" and you discard a Revitalize card, you're ok.
The problem I think you're running into is when a card has a condition inside it's own effect. I'll use the Set 26 Itachi as an example.
[Attacker | Mission] 0: Discard a Ninja. In that case, draw 2 cards.
Itachi's Cost is to pay 0 Chakra, and then his effect goes on the chain.
His effect is twofold. First, you Discard a Ninja. The second part relies completely on whether you actually completed the previous action or not. So, In That Case (If that Ninja was discarded), you draw 2 cards. If the Ninja was not discarded, you don't draw the 2 cards.
while youre here i know this has been answered but tp4 tenten, tenten uses in that case but you still draw if you discard a revitalize card I know it works but its a bit confusing when you try to explain why that works but why itachi doesnt