Why is vanilla so expensive?

 Vanilla comes from a plant that belongs to the orchid family, to a genus with more than 100different species. Evergreen perennials, they climb up trees, bloom for no more than a few hours and will only develop a fruit if they are pollinated by insects during the period.

 Because of its shape and leathery appearance, the fruit of Vanilla Plant
oil is called a pod, but the correct botanical term for it is a capsule fruit. It forms from the ovary and several fused petals, and bursts open after it has dried, spreading its seed.
            In the industrial production of vanilla pods, the flowers are artificially pollinated, and the green fruits are put through a drying and fermenting process that lasts for several weeks. Only in this way can the famous vanilla aroma develop from the primary chemical component, known as vanillin. The complexity of the production process also explains why vanilla pods rank among the world's most eagerly sought after spices.