I'd like to know the cost of staying in a hotel with washing machine service for one day.

Use the hotel laundry service. If you live in a homestay or youth travel, you usually have a self-service washing machine. If you stay in a star-rated hotel, you can use the hotel's laundry service. The price is around 30~60/piece, and the package is above 100. The advantage is peace of mind. Put it in a dirty pocket and deliver it clean the next day. The disadvantage is that it costs money. If you don't want to worry, just spend money to buy convenience. If you live in a homestay or youth travel, you usually have a self-service washing machine, some of which are free and some are calculated by kilogram, and the price is not too expensive. Is there a self-service washing machine? You can check it in advance when you make a reservation.