I was wondering the same thing.
Whatever the answer is -- and I think I might be able to guess -- I'd sure like to see some proof.
Some gas stations put a pie graph on the pump showing the breakdown of costs. Taxes is nearly 50%. There are a lot of steps along the movement of gas (from well to pump) where the gov't taxes the exchange, adding up to a lot.
Now consider that nearly half your income goes to taxes (state, local, etc.): kick around the math a bit, and you'll find it actually works out to you having to earn nearly $5 to buy a little over $1 worth of actual gas - the rest goes to taxes.