Saffron is expensive because it's hard to grow and harvest. It takes 300,000 flowers to make a kilogram.
Caviar is a rare delicacy made from sturgeon roe. It's expensive because the sturgeon fish takes decades to mature and the albino sturgeon is almost extinct.
Oysters were cheap, but overfishing and pollution made them expensive. Some people still pay a lot for them.
Rare, expensive, delicious white truffles are hard to find. One sold for $330k.
Black label Iberico ham is the best, made from pure-bred Iberian pigs, fed on acorns for 36 months. It's expensive, with a leg selling for £3,192.76.
Wagyu beef is expensive because of the strict rearing process. It's highly marbled and melts in the mouth. Kobe beef is the most prized, selling for up to £500/kg.
Kopi Luwak coffee, made from civet poop, can sell for up to $700/kg. Some say it tastes great, others say it's terrible. There are also concerns about the welfare of civets on farms.
Pâté made from force-fed goose or duck liver. Controversial. Banned in many countries.