Retail Stores

Alcohol is readily available at the major supermarkets: E-mart, Homeplus, and Lotte Mart. The size and selection of each supermarket's alcohol selection tends to vary. Convenience stores tend to carry a small selection, as well.

The cheapest alcohol is said to be at Costco. Although Incheon has a depot warehouse for shipping and distribution (probably due to its proximity to the port and airport), there is no customer warehouse. The closest location is by Yeongdeungpo-gu Office Station (영등포구청역) on Seoul Subway Line 1.

There is a chain of liquor stores called Kaja Juryu. Most of their stock consists of whiskies and cognacs.

Costco

Duty-Free

Cheap alcohol can also be found at the airport duty-free, after going through security. You can only buy alcohol with a departing ticket (it gets scanned by the store). It is not unheard-of to buy alcohol at Korean duty-free, drag it all over Bali, Phuket, etc, and then bring it back into Incheon.

You can use your point cards at the corresponding duty-free stores. L-POINT cards can be used at Lotte stores, etc.