The world's most expensive coffee is Kopi Luwak. It is planted in the excrement of an animal called the Luwak. This unique planting technique is responsible for its particular caramel taste, and it's selling price is between US$100 and $600 per pound.
It's produced in the Indonesian archipelago, Sumatra, Java, Bali, the Philippines and East Timor. World production is about a thousand pounds (450 kg) per year, hence the price tag. There exists only the Luwak and his special digestion system which can produce this coffee. The animal eats coffee beans, and when processed by its digestive system undergoes changes due to the presence of enzymes and gastric stomach juices that break down certain proteins, giving them a unique flavor.