at my expense

桐野 夏生の "Grotesque" を読んでいます。

He shouted at me, with breath reeking of boose, "Get the hell out of my face. I got a good buzz on and don't want you ruining it."
The hawkers in front of the cabaret saw this and had a good laugh at my expense. Then slapped each other on the shoulder and looked over at me, eyeing me derisively.

普通は "at my expense" だと「私の費用（自腹）で」の意味ですが、上の例ではそれでは可笑しい。　辞書を見ます。
・Oxford English Dictionary: if you make a joke at somebody’s expense, you laugh at them and make them feel silly
・Merriam-Webster's Online Dictionary: used of a joke about or laughter at a person that might cause embarrassment: Everyone had a good laugh at my expense.
・Cambridge English Dictionary: making another person look silly: Would you stop making jokes at my expense?

笑われているのは超美人でスタイルも抜群だったハーフのYurikoです。信じ難いほど落ちぶれたものです。