I bought this used car for a song.
  我买的这辆二手车物超所值

 

buy something for a song含义是花的代价不大，而买到东西却很合算。这个短语可能来自街头卖唱的艺人。他们做的是无本买卖，唱歌来换取生活所需。如果唱一支歌就能得到报酬，也就是没花钱而买到了，言下之意是非常便宜，等于中文里那句“物超所值”。
　　例句：
　　You have to be careful when you buy a used car. But I bought this 91Ford for a song, about half of what I expected to pay. And I've had good luck with it - it runs like a new car.
　　买旧车是得小心谨慎，但我买的这辆91年福特牌汽车真是物超所值，只花了预计中的一半钱。可我真走运，这车开起来就像新的一样。