Every practical way to make this trip, cheapest and simplest first.
At Gimpo Airport follow the Seohae Line signs rather than the Airport Railroad ones, then change to GTX-A for KINTEX Station. Come out at Exit 2, which opens onto Exhibition Hall 1 about five minutes from the entrance. KINTEX puts the whole trip at about 25 minutes.
about 25 min · about KRW 3,400 · Far and away the quickest way in, and the reason to fly into Gimpo if you can.
City bus 150 runs from Gimpo Airport to Daehwa Station on Line 3, and from there it is a 10 to 15 minute walk to the halls. It is an ordinary city bus with no luggage bay, so it suits a laptop bag rather than a suitcase.
about 54 min, plus a 10 to 15 minute walk · about KRW 1,650 · The cheapest option, if you are travelling light and not in a hurry.
Take a taxi from the rank outside arrivals and show the driver 킨텍스 or the address 경기도 고양시 일산서구 킨텍스로 217-60. Gimpo is much closer to KINTEX than Incheon is, so this is a short and reasonably priced run.
about 19 min · about KRW 17,000 · Landing with a stand crate, or arriving just before your show opens.
Gimpo is much the easier airport for KINTEX — under half an hour by rail against about seventy minutes from Incheon — so take the Gimpo connection if your itinerary offers one.
Incheon Airport (ICN) → KINTEX, Goyang/Ilsan →
Gimpo Airport (GMP) → KINTEX, Goyang/Ilsan →