It’s not surprising to think that way if you play the deck. That’s because the deck becomes just BAD if your draws were mediocre and you only have doomkin to play on that curve and not the board dragons to support it; so waiting for a turn to play it might not be a disaster.
However that intuition we get might be a ruse; 1 mana might in reality translate to “6 mana or more”; that’s because you lose 1 mana to play it and you lose 1 mana next turn that you would have gotten and you lose the -1 opponent mana X 2 doomkins.