There are several different varieties of coffee currently competing in the market for the title of “Rarest Coffee in the World.” That rarity often correlates with the price of the processed beans when they are ready for sale, but, of course, it has a great deal more to do with the way they are produced.
Most coffee beans grow together as pairs of seeds inside each coffee cherry, and take on a flattened shape. About five percent of the time, however, a coffee cherry will contain just one single, small, round bean, known as a peaberry. Some coffee connoisseurs maintain that these beans have a distinct flavor, but others disagree. Either way, peaberry beans are sometimes carefully sorted out by hand and packaged separately. Because of that effort and their relative rarity, they command a higher price. They do not represent the rarest type of coffee, but because they require much more labor in production, they are less commonly found.
Most coffees from around the world are processed in much the same way- the cherries are handpicked, the seeds are stripped out and dried, then roasted prior to packaging and sale. Certain varieties of coffee are handled a bit differently, with an extra step in the process: they are eaten first. Indeed, one of the rarest of all varieties, called Kopi Luwak, comes primarily from Indonesia, and is processed by Asian palm civets. These jungle cats eat the cherries, digest them, and excrete the beans. During digestion, the beans are processed by enzymes in the stomach of the civet, which alters their flavor. The beans are hand-collected and further processed normally, but because of their rarity, they often sell for hundreds of dollars per pound.
These coffee beans are processed in a similar way to Kopi Luwak, except that they are eaten by elephants, rather than civets. The elephants are from one specific reserve in northern Thailand, and there are about twenty of them that are used in the production of the coffee. The beans they produce are exceptionally rare due to a number of factors. Some of them are destroyed by chewing before passing through the digestive system of the elephant, and others simply aren't found by the workers who recover them. All told, it takes about 72 pounds of coffee cherries to produce just two pounds of beans in this way. They are sold almost exclusively to a small selection of five-star hotels in Southeast Asia, and the going price of the brew is about $50 per cup.