Saffron may well be the most expensive spice on earth, fetching as much as $150 per ounce. And in case you’re doing the math, that’s about $4.8 million per ton!

Why so costly? The source of this exotic spice is the stigmas of a crocus flower that blooms once a year for only a few days. Each flower must be picked and its three fragile stigmas removed from the center of its petals by hand—a very tedious process. It takes …