CNBC wrote in that 2020 about the cost-sharing agreement for US troop presence in South Korea
In the last one-year, cost-sharing agreement, Seoul agreed to pay roughly $900 million and in negotiations for the new one, they had offered a 13% increase on that number [...]. Those cost-sharing agreements, also referred to as the Korea Special Measures Agreement, have existed since 1991 [...]
It wasn't too clear that the time frame involved for the payments is, but I managed to find a later document:
The contribution of the Republic of Korea for 2020 is 1.0389 trillion Korean Won. The contribution of the Republic of Korea for 2021 is 1.1833 trillion Korean Won. The 2022, 2023, 2024, and 2025 contributions shall be determined by increasing the contribution of the previous year by the ROK defense budget increase rate of the previous year.
1 trillion won is approximately 800 million USD, so those contributions are (since 2020 at least) annual figures.
Looking for similar figures for European countries, I found an article about Germany:
Between 2010 and 2019, Berlin paid a total of €982.4 million, with €648.5 million spent for construction measures and €333.9 million defence costs, according to the finance ministry figures published in response to a parliamentary query from opposition Left Party lawmaker Brigitte Freihold (Die Linke).
Per year, that seems like 10% of what South Korea is now paying, while the US troop levels are somewhat similar (tens of thousands) in both countries. Is the German payment figure really cumulative over 9 years, and if it is why is that?
(It's been suggested in an answer-comment below that South Korea should pay much more per US soldier given the risk of North Korean attack. However, the formal structure of the US-SK costs sharing agreement doesn't seem to have anything like that explicitly factored in. The high-level breakdown is on labor-sharing, logistics-cost sharing, and in-kind contributions. Of course, as one might say, there are many ways to slice a price. So, if there is indeed an accounting trick that covers up for that, it should be explained in an answer, rather than merely conjectured.)