The prices of all products purchased in Korea include 10% VAT.
If you want to get a tax refund prior to departure, make sure to request Tax Free Form Receipt when you purchase a product worth 30,000 KRW or more.
As you can get a tax refund at a machine or a counter in Incheon International Airport prior to departure, make sure to refer to the Incheon International Airport website.
Incheon International Airport Website:
https://www.airport.kr/ap_lp/en/dep/process/vacref/vacref.do