I did a quick search because your stats intrigued me, I 'd remembered that the Korean war was only a bit more than Nam in GNP.
I didn't find much, in fact,
my google search brought me back to able to know with BBB's thread on the
history of what US wars have cost.
I have found many sites with drastically contradicting figures but I do know that the maintenance of troops in Korea over the last 50 years has cost much more than the actual war.
Since the war technically hasn't ended i wonder if Newsweek was including the running costs.