The most expensive brand of coffee in the world is Indonesian Kopi Luwak. A 50g taster of this coffee (whole beans) will set you back almost £15 if you order online. To give some perspective, a jar of instant coffee of that size would typically be between £1.50 and £2.
The real thing should say '100% certified'. So what makes Kopi Luwak so different from other coffees? The answer comes as a surprise to many people. This brand is made from coffee berries - the berries are eaten by civets, then pass through the animals' digestive tracts (only the pulp is digested, while the beans/berries keep their shape) having had any bitter flavours much reduced by the enzymes in the civets' digestive tracts. When the beans have been excreted they are collected and washed, then dried in the sun and roasted. The process is very labour intensive and only quite small quantities of coffee are produced - major reasons why the price is so high.