That’s definitely a problem; and quite possibly an uneconomic one for the lower value ores; but I would be quite surprised if it is the bigger problem. Building rail lines through some fairly unpleasant terrain was a pretty solidly solved problem by sometime in the 19th century, if not earlier, particularly if you don’t have to worry too much about worker mortality.(Indeed, it’s a problem that was actually solved more in the past than it is today in quite a few locations; mostly former colonies that used to have colonial overlords who realized that efficient exploitation required decent infrastructure.)
Pacifying Afghanistan hard enough to allow for construction to proceed, or keep the operations from being raided all the time is…much less solved…
