What is the richest city in South Korea?

Could you please elaborate on which city in South Korea is considered the wealthiest? I'm curious to know what criteria are typically used to determine the ranking of cities in terms of wealth, such as GDP per capita, average income levels, or perhaps the concentration of high-value assets within a specific region. Additionally, are there any notable industries or sectors that contribute significantly to the economic prosperity of this particular city, and how does it compare to other major urban centers in the country?