Iraq already to cost more than Viet Nam in half the time.
...Overall, he said, "we're easily headed toward $600 billion." That would top the $536 billion cost of Vietnam in today's dollars. World War II cost an inflation-adjusted $3.6 trillion.
In the end you can probably almost double the $600 billion projection.
And this is just direct costs as calculated by the government's dodgy accounting standards. Long term follow-on costs like care for disabled veterans will increase that number substantially.
Where does all this money go?
We had 500,000 troops in Viet Nam at the peak. We were bombing like crazy and had more high intensity combat operations. Yet we are already surpassing what it took 10 years to spend in Viet Nam.