回到你手上的好處
回程上載著好東西，這是最接近字面的一支。
noun · B2
The money, benefit or advantage that comes back to you from a business, a project, or something you have spent money, work or time on.
回報／收益
核心畫面
One way to hold payback: something goes out from you, and later something comes back along the same line. You pay, and it comes back. The noun names whatever arrives on the return trip, or how long that trip takes. Fill the return trip with money and you get a profit; fill it with the harm someone did to you and you get revenge; measure it with a calendar instead of a sum and you get a period of time.
payback 可以想成一條來回的路：東西先從你這邊出去，後來有東西沿著同一條路回來。這個名詞指的就是「回程上載的是…更多收起
payback 可以想成一條來回的路：東西先從你這邊出去，後來有東西沿著同一條路回來。這個名詞指的就是「回程上載的是什麼」，或者「回程要走多久」。回程載的是錢或好處，就是回報；載的是別人先加在你身上的那筆帳，就是報復；如果你量的不是金額而是時間，得到的就是一段期間。From the word’s history
Wiktionary records payback as a deverbal noun from the phrasal verb pay back. The two words are still visible inside it: pay, and back.
來源記錄 payback 是從動詞片語 pay back 直接轉成的名詞。pay（付）和 back（回去）這兩塊到現在都還看得見，這也是為什麼它的每個意思都繞著「回去／回來」這條線。
Wiktionary entry 'payback' (packet evidence kaikki:3f6f69a190036ae4:1157180410, etymology_text: 'Deverbal from pay back.')
Three branches
回程要走多久
同一條回程，但量的不是「載了什麼」，而是「走了多久」，所以答案是一段年數而不是一筆金額。
noun · C1
The length of time it takes before the money you put into something has earned back what it cost, so that you start to make a profit.
回本期
還回去的那筆帳
同一條回程，只是這次載回去的不是好處，而是對方先加在你身上的東西。
noun · B2
Something you do to someone to make them suffer, or to beat them, because of something bad they did to you earlier. In everyday American English it is often said lightly, about winning against a team or a friend who beat you before.
報復／討回來