noun
cash cow; gold mine; source of funds
Figurative expression for a person, product, or business that reliably generates a lot of money. Often used in business or entertainment contexts.
あのアイドルグループは事務所のドル箱だ。
That idol group is the agency's cash cow.
この商品は会社にとってドル箱になっている。
This product has become a gold mine for the company.
noun
cash box; safe
Literal meaning: a box or safe for storing money. Less common than the figurative sense.
店長は売上金をドル箱に入れて金庫にしまった。
The store manager put the day's earnings into the cash box and locked it in the safe.
Similar figurative meaning of a reliable source of income, but 金のなる木 is a more traditional Japanese expression, while ドル箱 has a modern, business-oriented nuance.
Compound of ドル (dollar) and 箱 (box). Originally referred to a box for storing dollar coins, then extended figuratively to mean a lucrative source of income.