I saw that about Trump wanting payment from South Korea upwards of $1billion for the THAAD system. He said, "I informed South Korea it would be appropriate if they paid. It's a billion-dollar system," Trump said. "It's phenomenal, shoots missiles right out of the sky."
But, it seems that the US military owns it. From the same Reuters article Pain posted a link to, 'A former U.S. State Department official estimated the cost of the system at about $1.2 billion but said the United States would not want to sell THAAD to Seoul.
"We want to retain THAAD in our arsenal, consistent with all other U.S. weapons systems deployed on the Korean peninsula. We own them. We retain them. We have the right to redeploy them," the official said, speaking on condition of anonymity.'
So...he wants another country to pay the US for something the US already owns? Isn't that a bit embarrassing?