Answer by
PZ (1206)
Truffles are expensive because they are in short supply. Truffles develop underground in association with specific tree roots. Black truffles from the Perigord region of France, for example, will only grow around oak trees. Specially trained truffle-sniffing pigs and dogs are used to find these delicacies, which are difficult to cultivate and thus must be harvested in the wild.