Gasoline - I'll buy 200 units\gallons at the current price please?

Why can't we go up to the gas station pump and buy 200 units\gallons on your gas debit card at the current value, so you are guaranteed that price?!?

We do it with books, computers, and many other products on-line, or at your local store , and sometimes EVEN get a discount on mass quantity! Can this 'supply chain product community' get its act together? And what laws prevent this? And why? Do we just say 'oh, ok' when our eyes glaze over about the technicalities, and why cant we make this happen? What 'special interest group' stands before you? A society, a threat...

The analysts talk about supply and demand, commodity trading with oil, and potential threats to the supply chain. Lets really level the playing field, and ALLOW the consumer to buy volumes of gasoline at current market price. Then we'll see the price of gasoline equalize...