
If a permanent is copying a melded permanent, the mana value of the copy is 0.

713.3b While the two cards of a meld pair are on the battlefield as a melded permanent, the object represented by those cards has only the characteristics of the combined back face, and its mana value is the sum of the mana values of its front faces.713.3a While a meld card is outside the game, in a zone other than the battlefield, or on the battlefield with its front face up, it has only the characteristics of its front face.The front face of each meld card and the combined face formed by a meld pair each has its own set of characteristics. The resulting permanent is a single object represented by two cards. To meld the two cards in a meld pair, put them onto the battlefield with their back faces up and combined (see rule 701.37, “Meld”). One card in each meld pair has an ability that exiles both that object and its counterpart and melds them. Its back face can’t be cast or put onto the battlefield, and it can’t transform or enter the battlefield transformed. 713.1b A meld card isn’t a double-faced card.Each meld pair consists of two specific cards whose back faces combine to form one oversized Magic card face: Midnight Scavengers and Graf Rats meld to form Chittering Host Hanweir Garrison and Hanweir Battlements meld to form Hanweir, the Writhing Township and Bruna, the Fading Light and Gisela, the Broken Blade meld to form Brisela, Voice of Nightmares.


A meld card has a Magic card face on one side and half of an oversized Magic card face on the other. From the Comprehensive Rules (October 7, 2022- Unfinity)
