Seoul Subway Map.
Fare - basic fare with cash : 1,150won ~ 1,800won (about 1$-2$) / adult)
** you can use the ticket machine in the subway station to buy one way ticket.
It costs 500won more than I wrote,
but you can get 500 won refund from the arrival station
to insert the card ticket(you got from the machine) in the machine
which is in front of the gate from the platform
in your final destination station.
(Don't forget!!)
** When you travel, actually you will hardly see the person using this ticket except travelers.
Because most of Koreans use T-Money cards.
T-money card is Korean transportation card.
With T-Money card, you can get almost free transfer between buses and subways.
the card cost 2.000won -5,000won(depends on the design)
and you have to charge the card.(from 5,000won~)
If you plan to travel Korea by buses or subways,
I think spend 2,000won(2$) and use almost free transfer system is better.
Later, I will upload more about transfer system in Korea.
Get More information about Korean Subway