I did some reseach for you, and have found the following. As in the first reply to your question a page was linked, it listed some prices but not the prices you were looking for.
In South korean they have something like the T-Money Card, you can add funds on this card to travel with it.
But they also have something else called the MPASS,
MPASS, is a transportation card exclusively for international tourists traveling in the Seoul metropolitan area and Jeju. The pass offers 20 rides a day for the duration of the pass. Additional funds can be loaded to MPASS and be used as a Tmoney card.
The prices for these cards vary on depending on the duration you want to have the card, it can be a 1-day card up till a 7-day card. The prices also vary a bit, I will mention them here, and also provide a link to the webpage where I found this.
Card Duration Price Discounted price (after 17:00)
- 1-day pass 15,000 won 12,000 won
- 2-day pass 23,000 won 20,000 won
- 3-day pass 30,500 won 27,500 won
- 5-day pass 47,500 won 44,500 won
- 7-day pass 64,500 won 61,500 won
The MPASS, can be used in the following areas:
Seoul: subway lines, airport railroad all-stop train, mainline buses,
branch buses, circulation buses, village buses, night buses
Jeju: Jeju city buses ※ Jeju pass can be used both in Jeju and in the
Seoul metropolitan area.
The ticket can also be bought at several locations like the airport, and in Seoul itself.
Incheon International Airport
- Tourist Information Center: Passenger Terminal 1, 1F, In front of Gates 5 & 10 / 07:00-22:00
- Airport Railroad Travel Center: Passenger Terminal 1, B1, In front of Airport Railroad All Stop Train Gate (purchase only) / 05:30-23:00
- Refunds at the airport can only be made at the Tourist Information Center.
- Seoul Station Tmoney Town : 1F, Seoul City Tower near Seoul Station (Seoul Subway Line 1, 4, AREX), Exit 10 / 09:00-18:00
- Myeong-dong Tourist Information Center: In front of Euljiro 1(il)-ga Station (Seoul Subway Line 2), Exit 5 / 09:00-18:00