Your high end seems to be about the same as the Saudis' "fair price." That is not a derogatory comment, I think they are more right than wrong about that. We need a price of about $75 to keep production stable, encourage development and provide an incentive to develop alternative sources of energy. I do think that the $75 target will change with the inflation we will likely see from all the economic stimulation around the world.
I have similar thoughts about NG prices.
But as we all know, the whole problem ultimately comes down to mismatches in supply and demand. Relatively marginal shortfalls or surpluses have dramatic price consequences across the entire production volume and dramatic effects on production levels. I see no easy solution to that since I am not in favor of mandated production levels or quotas. I guess a more rational system would price superfluous uses of energy more heavily than ordinary and necessary uses so that the brunt of the pain fell on socially problematic consumption (this is probably a charge gas guzzlers more for fuel in some fashion approach or have a special jet fuel price for private aircraft -- or mandate an end to both). But I don't see how we manage that either.