If oil were expensive, plastic would probably still be used in all the places it is used today because it is lighter and a large percentage of oil goes into the transportation of goods.

I actually don't have a problem with plastic, at least in theory. Oil exists in the ground. I don't see an issue with pumping it up, using it for a bit, and putting it back into the ground via a landfill. I take more of an issue with recycling where plastic is shipped overseas and makes its way into the waterways.