Why are Sages fair? Opinions wanted!

[The Panther]

Question for all: At what cost would you have to think twice about building sages in the first 40 turns of a game?

Like perhaps:
80 gold - Of course, build them by the boatloads!
110 gold - Probably build several when the gold starts coming in, for the research gets so much harder to make it to the higher and higher levels.
140 gold - Build a few because all you need is the lab to boost your research, but much prefer other choices.
170 gold - Never build one.

Any opinions?

They are still useful for the one random pick regardless of the research bonus. It is especially nice to get a blood sage when you are not a blood nation.

One other thing is that the other neutral mages sure seem FAR less common than sages. I would guess libraries have a higher probability to appear than other type sites.