the cost of the airplane ticket for the outward trip
the cost of the airplane ticket for the return trip
"行きのチケット代、帰りのチケット代"
the cost of the airplane ticket for the outward trip
the cost of the airplane ticket for the return trip
航空券代 the cost of the airplane, the cost of the airfare, あるいは単純に the airfare
でも大丈夫です。
行きの the outward trip,
帰りの the return trip
もっと堅苦しい、ビジネス的な言い方であれば、be incurred in ~を使い
the cost of the airplane ticket incurred in the outward trip
the cost of the airplane ticket incurred in the return trip