I think figuring out the “true costs” of petroleum use would be pretty speculative and almost certain to simply be based on political ideologies.
To what products do we want to attach the “costs” associated with plastic? Because it’s made of petroleum, do we attach the “costs” of plastic to gasoline, or only to plastic products? If one believes half of what one reads about the toxic effects of plastics in the environment, one would think it would be considerable. What about paint?
Grain production takes a lot of petroleum products, from diesel in the big tractor to the trucks that haul the grain to the fertilizers and herbicides that get applied to the fields, the trucks that haul those products, the machines that mill them, the trucks that carry the products around, the heat in the stores that sell them, on and on. Do we attach those “costs” to the cost of bread? To wheaties? To poultry? To the gasoline in the car of a woman who does everything in her power to “eat organic”?
Who, exactly, is getting “subsidized” because petroleum products are being used in producing them? All of them, and including the fellow who goes into a store and picks up a styrofoam flat of asparagus, wrapped in plastic wrap. He is being subsidized, I guess we’re supposed to think, because he isn’t paying the “true cost” of the problems caused by chemicals and fuels used to produce the asparagus, the toxicity of landfills, the death of dolphins who get their noses caught in plastic string, etc.
In actuality, to the extent anybody is paying the “true” (whatever that may be) cost of utilizing petroleum, everybody along the line is. Redistributing costs to, say, automobile drivers alone is simply an ideological preference aimed at punishing people who are presumed to be the culprits.