I just don't get how if when surfer uses his ability and discards a card, how professor x's ability works to make him discard the card that was already discarded. You pay the cost the instant you use it no matter what (like even if your opponent fizzles your finishing move, your character still exhausts). I understand people tried to explain the whole chain, but it still didn't make sense.

You're applying the right rule for the wrong situation. For payment powers, you pay all costs before the effect goes on the chain. A payment power can be easily recognized because it has an arrow (>>>) between the cost and the effect in the text box. Silver Surfer's power, however is not a payment power; it's a triggered power. A triggered power goes on the chain when it's trigger occurs. In the case of Silver Surfer, the trigger is the start of the combat phase.

At the start of the combat phase there is a priority point for both players to place effects on the chain starting the player with initiative. Triggered powers are placed on the chain before either player receives priority. Then, with or without a triggered power on the chain, the initiative player receives priority to play effects. He can add as many effects to the chain as he wishes before passing to his opponent. Then his opponent can add as many effects to the chain as he wishes.

Here is how the Silver Surfer and Prof. X situation would look. Let's say the Prof. X player has initiative. The Silver Surfer player has one card in his hand and it is a FF character card.

-At the beginning of the combat phase Silver Surfer's triggered power goes on the chain.
-the Prof. X player receives priority to add effects to the chain
-the Prof. X player pays one endurance to add Prof. X's discard ability to the chain
-the Prof. X player passes priority to his opponent
-the Silver Surfer player has no effects to add to the chain so he passes priority back to the Prof. X player
-after consecutive passes, last effect on the chain resolves and the Silver Surfer player must discard the only card in his hand
-the Prof. X player has priority to add effects to the chain but passes
-the Silver Surfer player has no plays so he passes back
-after consecutive passes the last effect on the chain resolves which is Silver Surfer's triggered power, but the Silver Surfer player cannot discard a FF character card so he doesn't get the effect in the "If you do" clause of Silver Surfer's triggered power

I hope this clears things up for you. If not, feel free to post what you don't understand or PM me and I'll get back to you.

-Bob

Discarding an FF character to steal initiative is part of Silver Surfer's effect.It is not an additional cost.

So if the effect have not resolved off the chain, Silver Surfer's controller does not discard the FF char card.

I think I finally got it. Thanks.