“give your right arm”别理解成“给你的右胳膊”，真实含义是不惜一切代价；（为了…）愿舍弃很多。

【例句】
What a voice! I'd give my right arm to be able to sing like that.
声音真好听，为了能够唱得那样好我愿意不惜一切代价！

I'd have given my right arm to have been there with them.
为了能和他们一起去那里，我愿意舍弃很多。