“Have you noticed that keyword price result in ZERO profit if there are no clicks? It’s cost/day (keyword price X clicks/day) that makes you rich, not keyword price itself.”
A top bid keyword, with low traffic, isn’t going to make publishers money. Also consider that many high paying keywords aren’t distributed to the content network, and that Googles’ smart pricing will adjust your percentage further still.
Good tip for Adsense: Keep traffic levels in mind.