If you choose the easy way in life, it often comes at a cost.
この場合は、to come at the expense of より、to come at a cost を使って言うと良いですよ。
ーIf you choose the easy way in life, it often comes at a cost.
「人生で楽な道を選ぶと、代償を伴うことがよくある」
to come at the expense of を使った例文:ーDrinking and smoking often comes at the expense of poor health later in life.
「飲酒喫煙は晩年に健康を害する代償をよく伴う」
ご参考まで!