at someone's expense
US /æt ˈsʌm.wʌnz ɪkˈspɛns/
UK /æt ˈsʌm.wʌnz ɪkˈspɛns/

1.
birinin masrafına, birinin zararına
paid for by someone; causing loss or damage to someone
:
•
The company party was held at the company's expense.
Şirket partisi şirketin masrafıyla yapıldı.
•
He made a joke at her expense, which made her feel uncomfortable.
Onun aleyhine bir şaka yaptı, bu da onu rahatsız etti.