at somebody's expense

at (one's) expense

1. Falling under one's financial responsibility. Once I learned that the trip was at my expense, I decided not to go.
2. To one's detriment or disadvantage. I was furious when I heard the other kids telling jokes at my little brother's expense.
See also: expense
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

at somebody’s exˈpense

1 paid for by somebody: When Joe is travelling at the firm’s expense, he goes first class.
2 (of jokes, etc.) making somebody seem foolish: They all had a good laugh at Pete’s expense.
See also: expense
Farlex Partner Idioms Dictionary © Farlex 2017
See also:
References in classic literature ?
a gentleman must be amused at somebody's expense!--I conceived the happy idea of disappearing.
It establishes a bond between the wit and the listener at somebody's expense. Comedy restores our wholeness.
I mean, he was capable of being very witty but almost always at somebody's expense. People were frightened of having their work criticized by him, and so on.