Right, but very unlike. The MtG standard for 3 red damage has actually a CMC2, with CMC1 being the exception to the rule (the case of Lightning Bolt in current T2, the limited Lava Spike, or Rift Bolt), and for 4 dmg it gravitates towards CMC3 (when the card is pushed, and always with a drawback associated, as in Char and that Shadowmoor RRR instant) and 4 (with the default being the simple Lightning Blast). Adding a mere point of damage dealing to a card involves a much more different math than add a point of life gain. That's the same premise that makes a point of creature power much more onerous in terms of costs than a point of toughness. The reason is simple: damage shortens the game, as life gaining prolongs it, and the later is more likely to afford interactivity than the former.