I remember when a cord of wood was about $35. Boy does that seem long ago now.
I bought up some extra charcoal when WM overbought. Great price. They were doing end-of-season sales on their propane (good for regular cooking) - but could not quite pull it off. Still there might have been a way. I still need to look.
http://solarcooking.wikia.com/wiki/Solar_Cooking_Wiki_(Home)
http://solarcooking.wikia.com/wiki/Category:Solar_cooker_plans - Quick and easy is foil covered cardboard.