How much did Vietnam war cost taxpayers?

Answer 1

That is difficult to compute as there were a lot of indirect costs next to the immediate expenses. Direct costs, the cost of war elsewhere, supporting and arming neighboring countries, veteran benefits and interest costs amount to something like one trillion US dollars. That is not counting the cost of the slowing down of US economic growth rates during the war and of the '70's crisis that followed: it would be very difficult to establish which exact elements of that slow-down and crisis were directly assignable to the Vietnam War.

A trillion dollars however seem relatively cheap compared with the cost of the Second Gulf War in Iraq and Afghanistan which has been estimated at around 3 trillion US dollars.