Around $20bn, or something over £14bn, if you prefer.
That is the latest estimate of the cost of rebuilding Afghanistan, once an internationally acceptable government has taken power in Kabul This figure is apparently based on the near £4bn that has already been spent over five years in Bosnia - about £700 per head of population. Once most refugees return, Afghanistan's population could reach 25M - the assumption seems to be that a 'third world' nation like Afghanistan will need less proportional help than a nominally developed country like Bosnia.
This is rubbish. After decades of war Afghanistan is lacking even the most basic physical, social or legal infrastructure.
Compared to Bosnia or Kosovo, the country is a primitive wilderness, scourged by drought, shattered by the scorched earth lunacy of the retreating Taliban.
Over much of the country total ecological collapse is a real and imminent possibility.
The world has to accept that the land is incapable of providing anything more than the most basic subsistence existence to most of its benighted population. If generations of Afghans are not to spend their entire lives as inmates of permanent refugee camps, dependent on international handouts, a massive reconstruction programme has to be launched immediately.
And when the final bill is totted up, when the costs of mine clearance, training police, judiciary and educators, etc, are added to the cost of building an entire infrastructure almost from scratch, it will come to a lot more than £700 per head.
But even if the cash is forthcoming, and most of it is used for its intended purpose rather than siphoned off to pay for some warlord's re-armament programme, will it actually achieve a better life for the average Afghani?
The challenge is enormous.
Nearly 80% of the population has no access to clean water, nearly 90% live without adequate sanitation. Thousands of homes are badly damaged or destroyed, irrigation systems and wells no longer function, roads, bridges, power stations and hospitals have been mauled by high explosive. It will take decades to bring Afghanistan to the minimum standards acceptable to the civilised world - even longer if we repeat the mistakes of earlier development programmes.
What is needed is appropriate or intermediate technology, not high-tech Western solutions that will leave the country dependent on Western imports.
Over centuries Afghans have developed ways of living in a harsh terrain - these need to be further developed rather than replaced with alien alternatives.
Mud housing may sound medieval but modern rammed or stabilised earth construction would be a logical and more durable alternative. Reed beds and slow gravity sand filters would go a long way towards solving sanitation and water problems. And as the Romans (and General Wade) have shown, unbound roads, properly maintained work; certainly better than modern alternatives no-one can afford to maintain.
Other intermediate technologies exist, from the hydram pump to the solar cooker. All should be considered seriously.
If Afghanistan is ever to enter the 21st century, the alternative route just might be the quickest.
Dave Parker is NCE's technical editor