Transportation seems to be quite expensive when traveling to South Korea. How do you solve the transportation problem?

I made a reservation for my independent trip to Korea last year through Zhongxin, and they gave me a book called "Xing'er Takes You to Travel in Korea". There was a card in the book with the symbol of "Free Travel to Korea" on it, which should be T-money~ If you want to buy it, you can buy T-money at convenience stores or newsstands with the T-money logo, subway stations, etc. The basic fee for a universal transportation card is 2,500 won. At the time of purchase, the amount stored in it is zero. You can recharge the card from 1,000 won to 90,000 won at a time. When you use the T-Money card to pay for transportation, you get a discount of 100 won than using cash. You can also get discounts when transferring. Using T-Money card - If you take the subway with a money card, as long as the route is not too long, the one-time cost is basically 1,050 won. The basic fee of 2,500 won is non-refundable, and the card can only be used as a souvenir. You can also pay at GS. Taking a taxi in South Korea is very expensive. Overall, the subway and bus are more economical. The subway is convenient and the bus is cheap.