Which expensive spice is made from crocus flowers?

There’s a good reason saffron is so expensive. Saffron threads are the stigmas found in the center of the Crocus sativus, a purple flower in the Iris family that’s better known as the saffron crocus. There are only three of the orange-yellow stigmas in each flower, which means it takes a lot of flowers to make a little bit of saffron. Each pound of saffron contains between 15 and 20 thousand stigmas.

Source: Reader's Digest