The price of crude is only a fraction of the price of gasoline. The cost of transporting the crude, refining it and distributing it to the end user hasn't changed.
Plus all the state and federal taxes are fixed per gallon regardless of the price per gallon.
Federal tax is 18.5 cents per gallon. State taxes are tacked on top of that. Texas adds an additional 20 cents per gallon. California adds an additional 50 cents.