In this file photo from July 16, passengers board subway train on Line No. 2 at Gangnam Station in Seoul. Newsis

Seoul Metro has earned about 15 billion won ($11.4 million) in profit from selling the rights to subway station names, thereby allowing them to possess alternative names, over the past four years, according to the company Sunday.

The subway station that made the largest profit was Gangnam Station, also known by its alternative name, Haru Plant Dental Clinic, with a contract of 1.11 billion won.

Since 2016, Seoul Metro has started auctioning off station names to help it overcome financial difficulties.

These names are displayed alongside the original station names in brackets and are used during announcements on the trains and at the stations, as part of a three-year agreement that can be extended only once.

Of the 276 stations on subway lines 1 to 8 managed by Seoul Metro, 39 have alternative names as part of paid agreements. Through this project, the company reportedly generated 14.97 billion won in revenue over the past four years, averaging 3.7 billion won annually.

A business seeking to acquire the naming rights for a station must be located within 1 km of the target station and and should choose a name that is suitable and appropriate for a public space.

Among the businesses that meet the criteria, the one with the highest bid secures the station name.

Following Gangnam Station (Haru Plant Dental Clinic), the next highest was Seongsu Station (CJ Olive Young) at 1 billion won, followed by Euljiro 3-ga Station (Shinhan Card) at 874.5 million won, Euljiro Entrance Station (Hana Bank) at 800 million won, and Seonneung Station (AQion Savings Bank) at 751 million won.

Additionally, the top 10 included Yeoksam Station (Center Field) at 705 million won, Euljiro 4-ga (BC Card) at 770 million won, Myeong-dong Station (Woori Financial Town) at 654.66 million won, Guro Digital Complex Station (Wonkwang Digital University) at 477 million won and Apgujeong Station (Hyundai Department Store) at 473 million won.