Do not rely on bus cash
VISITKOREA’s Jeju guidance says city buses no longer accept cash. A cash budget is still useful elsewhere, but it is not a substitute for preparing a usable transport payment method before boarding.
The Climate Card does not follow you
A Seoul Climate Card is not a Jeju pass. If the calculator recommends Climate for Seoul and the trip includes Jeju, the complete setup still needs T-money or another accepted Jeju transport payment method.
Treat express and special services separately
Nationwide card acceptance does not mean every tour, airport transfer or reserved service uses the same fare. Confirm special services with the operator and keep the finder focused on ordinary public transport.