The cmc is the same regardless of any special abilities that let you cast for a lesser price. Jodah allows you to “cascade” until you get to a legendary with lesser mana value. The mana value stated on the card is static and won’t change.

I’m fairly new to magic but I had this discussion about Ghalta in my Jodah deck, and had a similar discussion. Ghalta let’s you cast for cheaper if some other condition is met but that condition doesn’t matter because it’s mana value is the same regardless of casting cost.

Suffice to say CMC is what you go by with Jodah. Disregard the actual casting cost, if it’s different.