at the cost of

We must cherish experience acquired at the cost of blood.

我珍惜用鲜血换来的验。

He rescued the boy from drowning at the cost of his own life.

他救这小孩免于淹死却牺牲了自己的生命。

The poor fox escaped from the trap at the cost of a leg.

那只可怜的小狐逃出了陷阱, 却失去了一条腿。