Oh Young-jin over at the Korea Times seems to have a better understanding of President Trump than the rest of Korea:

Let’s calm ourselves down.
It’s exasperating to hear U.S. President Trump demand South Korea pay $1 billion for a missile interceptor owned and operated by the U.S. After all, the two allies cut a deal by which Korea provided land for a Terminal High Altitude Area Defense (THAAD) battery, while the U.S. paid for the rest ― hardware and maintenance.
It’s tempting to shout back at Trump and tell him that we don’t want it so he can take it back.
But here are some sobering questions.
Can we defend ourselves without U.S. forces? The South excels the North in the size of economy many times and is more than double it in terms of population. So the answer to this question is yes, we can.
But if so, what extra cost would we have to pay for their absence? Billions of dollars would be needed to make up for the U.S. Forces Korea with its 28,000 American troops stationed here. They serve as a tripwire to bring in bigger and more powerful reinforcements ― the so-called extended deterrence (nuclear umbrella) included ― from the U.S. in the event of a war. The tab for this is uncountable because it has worked as the bedrock for Korea’s sense of security for decades.
Would you be willing to pay that extra cost? The bulk of the budget for welfare, infrastructure and other key state affairs would have to be diverted to cover our own defense spending. This means bigger tax bills for fewer services. Then, the security void that would be created by the U.S. withdrawal would have foreign investors rethink their plans involving Korea.
THAAD can turn this chain of hypotheses into reality. (……….) Now, it is important to think of how Trumpian arithmetic works.
Trump is a “successful” businessman and showbiz celebrity.
Therefore, he shuns money-losing businesses and sticks to the “beneficiary-pays” principle. This characteristic reflects his demand for Korea’s THAAD payment as he sees the U.S. as a benefactor and Korea as a beneficiary so he thinks it is natural for Seoul to pay. [Korea Times]
You can read the rest at the link, but Mr. Oh advocates for paying Trump off by having a pro-rated cost for use of the THAAD system each year. This gets back to my belief this whole topic is about the USFK cost sharing negotiations next year which President Trump wants the Korean government to understand they need to pay more for advanced US capabilities.
By the way I still love Mr. Oh’s email: foolsdie5@gmail.com.