Please be aware that Seoul has multiple airports and that these results are for all airports serving the city.
The best month to fly between Seoul and Busan is March and the most expensive month to fly is February. (Average prices, based on 374 datapoints.)
The best day to arrive at Seoul is Thursday and it would be best to avoid Sunday, as prices are on average 91.11% higher than on Thursday. (Average prices, based on 264 datapoints.)
The cheapest airline flying from Seoul to Busan is Tway Airlines. They are 37% cheaper than Korean Air. (Average prices, based on 386 datapoints.)