for a song   (TTS發音)

at a low price ； for a bargain price ；cheaply低價；廉價

    He sold the invention for a song but its buyers are the ones who get rich. 他廉價賣出了新發明，買主卻發了大財。

    Now watermelons flood the market and can be bought everywhere for a song. 現在市場上到處是西瓜，在哪兒都可以很便宜地買到。