There is no difference between dried plums and prunes. They are the same thing. By definition, a prune is a dried plum. However, prunes cost more, and sometimes a lot more, when they are called ‘dried plums.’ At the Safeway store in north Berkeley, dried plums cost almost twice as much as prunes of the same size and type. Prunes cost $3.00 a pound, but dried plums cost $5.00 a pound.  Why are dried plums so much more expensive than prunes? That is easy to answer. People are willing to pay more for prunes when they are called ‘dried plums.’ Consumer testing has shown that people do not like the sound of the word ‘prune.’ People associate the word ‘prune’ with something that is dark, old, and wrinkled. Prune companies are acting rationally. Suppose you owned a prune company and you knew you could get $3 a pound for your ‘prunes’ or $5 a pound for your ‘dried plums.’ What would you call them? There are a lot of other supermarket products like this. For example hazelnuts and filberts are the same thing, but in California, hazelnuts cost more than filberts, whereas in southern states, filberts cost more than hazelnuts.