This article uses so many words to focus on the political reasons, but completely ignores the primary driver: Cost.

Korean weapons systems are 40-60% cheaper than their American counterparts.

The Korean K9 Thunder 155mm self-propelled howitzer costs $3.5 to $4 million per unit. For comparison, the American M109A7 Paladin costs around $8 million. The German PzH 2000 runs approximately $7 to $8 million.

The K239 Chunmoo Rocket Artillery (MLRS) system runs $2.0M/unit; M142 HIMARS runs $4.5M/unit. 155mm artillery shells are $2k/shell from Korea vs $3.5k/shell from the United States. Korean Cheongung II SAM interceptors cost ~$1.1M/unit, US Patriot missiles cost $4.0M/unit.

Buying South Korean weapons systems means you can procure twice as much at the same cost. It's a no brainer why Korea is winning military contracts.

[0] https://militarymachine.com/k9-thunder-howitzer-most-exporte...

Cost is a factor, and a significant factor, but not the only one.

Flip-side of cost is effectiveness, and it would be interesting to see real-world data on the accuracy, reliability, and longevity of Korean weapons systems in active combat. I suspect the Koreans are also anxious to see this given their own geopolitical situation and northern neighbour. The article doesn't go here either.

It does, correctly IMO, focus on the reliability of the US as arms supplier, given the increasing control over access as a political weapon of retribution and reward, potential "kill switches" in US arms, the limited total production capacity of the US, and particularly in light of the latter, stocks depletion and unavailability on the basis of capricious gallivanting into ill-conceived conflicts with little gain if not actually worsening its subsequent position, strength, and status.

The Koreas both have an extensive reliance on artillery. Seoul is within range of PRK batteries, Pyonyang not so much from ROK, but any invading forces would be. I suspect ROK counterartillery systems are well developed, and that given the effectiveness of drones in recent years and the likelihood PRK might rely on these that there are, or soon will be, effective countermeasures against them.

Antiballistic missile systems would also be useful for ROK. I know nothing of this, but find that there is a Wikipedia article on the topic: <https://en.wikipedia.org/wiki/Korean_Air_and_Missile_Defense>.

This is also the case for things like nuclear reactor construction, except South Korea is cheaper by a far higher margin there.

Add in the US's latest antics about controlling the use of they weapons they sell, and in addition trying to bully and demean allies, and it's a mystery as to why anybody would ever use US suppliers these days.

They also tend to license IP or subsystems to and from the US as well, similar to Israeli firms like Elbit so there is an incentive for the US to continue supporting Korean sales as they have a downstream positive impact on American suppliers (eg. Borame and GE Aviation as well as Lockheed Martin).

The majority of military hardware costs are bribes, kickbacks and margins. Nobody thinks that they will fight a real war in which they will need a lot of hardware.

If the US or Germany get in situation they need thousands of those - I guess their cost will fall to under 1M.