Shouldn't a Rainbow mage cost as much as a Bless Effect or Competent SC pretender?

I mean, is everyone overlooking the tremendous advantage of gem income if they are able to Last long enough to use it?

It's been said and I believe firmly that a Rainbow Pretender is useful if you are allowed the time in order to get the gem income up where you want it to be. The advantage in forging and rituals is significant mid-late game.

Why shouldn't rainbows cost as much for such an advantage?

Note: I am in favor of either A.) Giving them special abilities or B.) Lowering their cost by a moderate degree but I don't think that everyone should be playing Rainbows or have that as the only option with Human pretenders. I think that is the reason that they are so unappealing, because you can neither have a bless effect or a combative pretender with them. Only rainbows.