special fare; special rate
Used for discounted or promotional fares for transportation, especially air tickets and trains.
I bought this plane ticket at a special fare.
Please check the conditions for the special rate.
割引運賃 explicitly means 'discounted fare', while 特別運賃 can include promotional or special-condition fares that may not be simple discounts.
通常運賃 is the regular, standard fare, contrasting with 特別運賃.
Compound of 特別 (special) and 運賃 (fare, transportation charge).