In German, we have a phrase "jmd. in die Tasche spielen", literally "to play into someone's pockets". I am looking for a fitting English equivalent.
The phrase means, you are causing a third party financial gain with your actions. These words are nearly always used in a negative context.
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In a story, a character is asked to do a small favor, but by doing so an unnamed third party would gain money. Sarcastically, he responds: "Sure, I'll play into their pockets".
I'm looking for an actual phrase that keeps the meaning but is valid English.