Al of the grain products you are purchasing where produced over the summer and fall when diesel was still high. A fair amount of that grain was probably already sold during the spring on grain contracts, when people where offering $4/bu + for corn to guarnte the grain that they would need at that set price rather than the potential cost of fuel driving th open market price higher at harvest time. Since those grains where already bougnt at that price, the end comodity will still be at the higher price to cover the contract it was purchased on.
Remember is not just the grin used for bread, also the cattle feed for the beef and milk, chicken feed for the eggs and KFC extra crispy goodness, ect.