What is the Goldilocks Price for Food?

Over at Global Dashboard, David Steven asks a serious question by juxtapositioning FAO's views when food was cheap (a bad situation as it dampened income, innovation and employment) versus its views when food became more expensive (also a bad situation as it forces millions into chronic hunger).

Is there a "Goldilocks"  price for food?  If not should innovation policy and food supply for those in the greatest poverty be to some degree counter-cyclical?  Keynesian food policies, anyone?