You’re not taking onto account that portion of the per gallon price that will never go down, because it is excise tax levied at multiple levels of government.
They could give the gas away free from the point of view of the producers, and that per gallon tax would be the same as if the total price per gallon was $5.00.
I actually added in my post that taking into account all levels of taxes it seemed high still.
Maybe I better go check my math again :)