I think you need to include energy cost in the preparation stage. Bread requires a hot oven, which is a real amount of electricity

it's close to $0.40/kWh where I live. From this link it says that a bread maker uses only .36kWh, but an electric oven would be more like 1.6kWh. So bakita single loaf of bread, you end up with a not insubstantial fraction of the total cost going to heating the oven.

Of course, many bulk foods require heat, so it gets a little sticky this way. Oats/oatmeal probably wins out here, as you can just soak them overnight.