Last summer, on my way to a hotel near Incheon International Airport, I took a taxi from the airport. I was charged 5000 won despite a fare calculator displayed 4400 won*1.
Since I don't know how to negotiate demanding the change with the driver in Korean, I gave up 600 won.
(By the way, after that, I found free shuttle connecting the hotel and the airport)
In order not to be a second victim, please refer to the article.
*1:I don't remember the exact fare. It may be ranging from 4200 won to 4500 won.