I assume it to be zero, regardless of the fact that you pay 3 and regardless of the cards actual mana cost.
Am I wrong? I looked here for help.
From Comprehensive rules:
502.26. Morph
502.26a Morph is a static ability that functions in any zone from which you could play the card it’s on, and the morph effect works any time the card is face down. “Morph [cost]” means “You may play this card as a 2/2 face-down creature, with no text, no name, no subtypes, no expansion symbol,
and no mana cost by paying
rather than its mana cost.” Any time you could play an instant, you may show all players the morph cost for any face-down permanent you control, pay that cost, then turn the permanent face up. This action does not use the stack. (See rule 504, “Face-Down Spells and Permanents.”)
502.26b To play a card using its morph ability, turn it face down. It becomes a 2/2 face-down creature card, with no text, no name, no subtypes, no expansion symbol,
and no mana cost. These values are the copiable values of that object’s characteristics. (See rule 418.5, “Interaction of Continuous Effects,” and rule 503, “Copying Objects.”) Put it onto the stack (as a face-down spell with the same characteristics), and pay
rather than pay its mana cost. This follows the rules for paying alternative costs. You can use morph to play a card from any zone from which you could normally play it. When the spell resolves, it comes into play with the same characteristics the spell had. The morph effect applies to the face-down object wherever it is, and it ends when the permanent is turned face up.
502.26c You can’t play a card face down if it doesn’t have morph.
502.26d Any time you could play an instant, you may turn a face-down permanent you control face up. To do this, show all players what the permanent’s morph cost will be when the effect ends, pay that cost, then turn the permanent face up. The morph effect on it ends, and it regains its normal characteristics. Any abilities relating to the permanent coming into play don’t trigger when it’s turned face up and don’t have any effect, because the permanent has already come into play.
502.26e If a face-up permanent is turned face down by a spell or ability, it becomes a 2/2 face-down creature, with no text, no name, no subtypes, no expansion symbol,
and no mana cost. These values are the copiable values of that object’s characteristics. (See rule 418.5, “Interaction of Continuous Effects,” and rule 503, “Copying Objects.”) The rules for morph and face-down permanents apply to it normally.
502.26f See rule 504, “Face-Down Spells and Permanents,” for more information on how to play cards with morph.
Now I realize that I seem to have answered my own question, but a buddy of mine played a Morph against a "Protection from Converted Mana Cost of 3 or greater" guy from Future sight and this discussion came up.
I think converted mana cost of a morph is 0, he says "But on Magic Online it treats morph as CMC 3"
1) Morphs have converted mana cost of 0 with regards to Mana Drain, Chalice of the Void, Pyrostatic Pillar and protection from CMC 3 guy, right?
2) is this a glitch on Magic Online? I don't play onloine (other than MWS), but I'm sure that some of you do and can let me know if there are indeed glitches, or whether or not Magic Online's rules treatments are canon (beyond misclicking and such).
EDIT: 3) Are there other such glitches that I/he should be made aware of?
Our local shop finally got sactioned, and we want to play by the rules, you know?
EDIT: 4) by buddy now says it pertained to Repealing a Morph creature. He is now unsure of whether or not it costed 3U or whether or not it was another virtual magic card entirely.
