Saffron costs more per gram than gold

Saffron — the dried stigmas of Crocus sativus — costs between £5 and £15 per gram at retail, compared to gold at roughly £60 per gram. But by weight of comparable culinary utility, saffron is among the most expensive substances on Earth. Each flower produces just three stigmas, which must be hand-harvested within a few hours of blooming. It takes 150,000 flowers to produce one kilogram of saffron. Iran produces over 90% of the world's supply. A single gram can flavour and colour a large pot of risotto, paella, or biryani — dishes where no substitute replicates its flavour and distinctive yellow colour simultaneously.

Source: Willard, Saffron: The Vagabond Spice (2001)