A good hotel close to Hongdae Area is Holiday Inn Express Seoul Hongdae (rated 8.7/10 from 1,421 reviews).
For a good hotel near to Seoul Station, consider Shilla Stay Seodaemun - it is rated 8.1/10 from 1,490 HotelsCombined reviews.
Close to COEX Mall you will find Glad Gangnam Coex Center, which has a rating of 8.3 over 1,833 HotelsCombined reviews.
Searches in the last 72 hours suggest an average price of around $0/night is normal for a hotel in Suseo-dong.
Prices for Suseo-dong hotels have been found for as low as $0/night over the last 3 days.