Former US Ambassador Mark Lippert was well timed to mention that South Korea picks up about 55 per cent of non-personnel costs for the US military and pays for more than 90 per cent of the Pyeongtaek base, the largest overseas US military facility where key units will be relocated. South Korea is also the only country that provides support personnel - the Korean Augmentation to the US Army - for which the Seoul government spends about 10 billion won each year.

One more thing to note when one counts "defence surplus and deficit" is the fact that South Korea is a major purchaser of US arms, having spent 36.4 trillion won on weapons and military equipment over the past 10 years.

https://www.straitstimes.com/asia/east-asia/south-korea-pays-more-than-peanuts-to-host-us-troops-the-korea-herald