Copying spells

[Avodroc13]

 {Curse of Echoes} is on me and opposing player has all his mana tapped.
I play  {Fireball}, with 5 mana as "x", does my friend have to pay mana for "x" to copy it?
Or does he copy it with the mana I used?

[Keyeto]

Nobody has to (or can) pay mana for the copies spells. The copies are created on the stack with the same characteristics as the original. If you cast {Fireball} with X = 5, your opponent gets a Fireball with X = 5.

From Gatherer:

1/22/2011   If the original spell has an X whose value was determined as it was cast, each copy has the same value of X.