The reason why the Shinbundang Line fare is so crazy

The Shinbundang Line is run by different companies for each section, so if you go over even one station, additional fares apply.

In other words, there is no additional fare for the Gangnam-Jeongja line.

If you exceed the deposit amount, an additional fee is charged.

Because of this, if you use Gwanggyo-Sinsa, you will get the full fare because it goes through all the railroad companies operating on the Shinbundang Line.