Why is Heroin cheaper in Afghanistan?

Afghanistan is the world's leading producer of poppy (not poopy), the main and most important ingredient in heroin. Poppy seed is the nation's largest export and is a yearly 4 billion dollar business, the biggest agricultural market in Afganistan. With such high supply of poppy seeds, the legalization of its sales (the poppy seed) in Afganistan, and the low expectations of profits for poppy seeds by the farmers due to competition with others and the country's overall poor living condition, poppy seed is sold realatively cheap in Afganistan. It can also be noted that since most countries forbid the use, distribution, possession, and trafficing of poppy seeds, the only people who will buy poppy seed are heroin producers, users, and drug-dealers which add up to a realatively small amount of people even on an international level. Adhering to basic economic concepts, when there is a small demand for a product and a large supply, that product's price will be much cheaper, as it is in Afganistan.