"From the figures above, can anyone tell me just what we're defending South Korea from?"

China.

N Korea is a client state of China.
China doesn't want to border a rich Korea, and has the poor N Korea as a buffer for them. That N Koreans eat grass isn't a problem for Chinese.

The only way to solve N Korea is thru China, because they are their masters.
The N Korea leadership eats Chinese shit and smiles and ask for seconds, and this disgrace isn't a problem for the Chinese. N Korea is sewage plant, graveyard, and generally a scapegoat for Chinese who laugh every day at how stupid the N Koreans are. And N Koreans imagine that they are the most brilliance of negotiators.

Vast stupidity on both the Chinese and N Korean side- proud people who whore themselves for a nickel.