A few billion to recover a few trillion in mineral deposits is "good business". According to Wikipedia (and I remember reading about this on DU a year or so ago):
Mining in Afghanistan
As of 2006, "the mineral resources of Afghanistan were relatively underexplored from a global perspective. The country has extensive deposits of barite, chromite, coal, copper, gold, iron ore, lead, natural gas, petroleum, precious and semiprecious stones, salt, sulfur, talc, and zinc. Precious and semiprecious stones include high-quality emerald, lapis lazuli, red garnet and ruby.
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Major findings, 2010
In 2010, a small team of Pentagon officials and American geologists discovered about $1 trillion in untapped mineral deposits in Afghanistan, enough to fundamentally alter the Afghan economy and perhaps the Afghan war itself, according to senior American government officials. According to other reports the total mineral riches of Afghanistan may be worth over $3 trillion US dollars. "The previously unknown deposits including huge veins of iron, copper, cobalt, gold, and critical industrial metals like lithium are so big and include so many minerals that are essential to modern industry that Afghanistan could eventually be transformed into one of the most important mining centers in the world". Ghazni Province may hold the world's largest lithium reserves.
Of course, what will happen if they do manage to quell the violence long enough to get massive mining operations under way will be to strip-mine the country and leave them just as poor and destitute as they are now. We'll steal it all and give them a pittance in return for letting us take those minerals off their hands...