Transport Costs
I have no sympathy at all with the refusal to answer in full the FOI requests. However the price paid for each tonne of salt is dependent on two factors: the cost of the raw material at the point is is extracted from the ground and the cost of transport to the council depots. For a bulky, dense commodity like salt the transport cost will form a large part of the total cost and councils with depots a long way from the site of production will have to pay more than those closer. Not a reason to avoid answering the question though!