Does anyone know how fuel pricing actually works?

can someone explain how fuel pricing works. i have been on websites and found that all the major importers of petrol to australia say they can explain but just then go on to blow smoke out there bum.the only type of info they have is how much they are selling to the actual servos ( terminal gate price ) which very rarely changes in price..... so any answers would be great. oh and i work at a servo so no im not just bashing servos i really want to know as the employees get told nothing on how it all works.