Arguing that building a Trans-Afghanistan pipeline is uneconomic today misses the point. The value to US energy corporations is in controlling the rights to constructing the Trans-Afghanistan pipeline and thus a major road to the world's fourth largest supply of natural gas.
While there may or may not be value in contructing a Trans-Afghanistan pipeline today, there is HUGE value in controlling the rights to that pipeline, which the US now does through its henchman Karzai.
It is said "3 countries would like this project to exist. Turkmenistan would like to have an alternative to Russia to sell its gas to, Afghanistan would like the transit revenues it would bring, and Pakistan does need gas and this is one of the options."
Add a fourth, the US on behalf of its giant energy corporations.
Natural gas is an increasingly global commodity due to LNG. The cost of producing NG from the Rockies and various shale projects around the US is high and would be unprofitable (margins are already being squeezed due to oversupply) were the world maket to be flooded with more cheaply extracted & shipped NG from Turkmenistan via an Afghan pipeline.
The value of the Afghan pipeline is not in its immediate construction and operation, it is in controlling the rights to the road to market from the Turkmenistan gas fields to people who want to buy gas. NG is increasingly, and will continue to be, the fuel of choice. Controlling access to the world's fourth largest supply of NG is valuable and pays dividends today to those who are in the business of supplying NG whether or not the pipeline is built now or 50 years from now.
While it might have been economically desireble to build a pipeline in 1997 or even 2005, the value to US energy giants today may very well be in insuring that the pipeline does not get built until conditions suit them to have it built. Not building a pipeline costs little, obtaining & retaining on behalf of US energy multi-nationals the rights to build or not to build has cost, and continue to cost, US taxpayers, US service men and women, and Afghan civilians plenty.