Historical Rules · 18 February 2022
Rule 202.3c
Official source text from the 18 February 2022 Rules release
The mana value of a melded permanent is calculated as though it had the combined mana cost of the front faces of each card that represents it. If a permanent is a copy of a melded permanent (even if that copy is represented by two other meld cards), the mana value of the copy is 0.