We must also consider the alternative that many of the most prominent and powerful Afghans are in fact motivated by greed and opportunism. [harrowell: ya think?] It is therefore in their interest to maintain the status quo of massive US and international spending that fuels the Afghan "rentier state" economy.
This isn't just recreational cynicism; they argue that the latest announcement of a clampdown on private security companies in Afghanistan is to be taken more seriously than the last six, and that this actually represents an effort to integrate them into the Afghan government's forces or at least its allies. Importantly, and very differently from Iraq, the main players are local rather than foreign - like the 24,000-strong Watan Group. (Check out their Corporate Social Responsibility page.) Rather than just being part of the ISAF baggage train, they're a significant nonstate actor in Afghan politics.
If you were feeling optimistic, you might consider this as being similar to the various political fixes the Soviets arranged in 1988 to keep the roads open for the Afghan government post-withdrawal. If you've been reading this since at least 2007, you'll know that I think the absolute best that could happen in Afghanistan would be to get back to something like the 1989-1992 period, just without the continuing US/Pakistan/Saudi destabilisation and the cut-off of Russian aid that kicked off the civil war (and the destruction of Kabul, the invention of the Taliban, and so on). I agree this is pessimistic, but then, well, I wouldn't start from here.
In Iraq, understanding the business/organised crime environment may have played a bigger role than is publicly acknowledged in getting the US Army out of town. For example, here's a Joel Wing piece on the history of oil-smuggling (you'll note that the Baiji refinery comes up. party like it's 2005!). Interestingly, the initial Awakening Council leader Sheikh Abu Risha was an important oil smuggler, and you can bet those networks were of use.
Leaving aside the obvious Afghan export, the analogous business is probably selling stuff to ISAF. Bagram now has its own cement plant, inside the perimeter, but that's a Turkish construction firm.