The impulse buy

On a whim, I bought a piano: an antique Wurlitzer spinet. Or is it just old? I'm not quite sure when an old thing becomes an antique. Regardless, it's very old, and very graceful, and the notes are ever so slightly off, and my children love it.

And, appropriately enough, I got it

for a song
idiom
Very cheaply, for little money, especially for less than something is worth. This idiom alludes to the pennies given to street singers or to the small cost of sheet music. [Late 1500s]
"for a song." The American Heritage® Dictionary of Idioms. Houghton Mifflin Company, 1992. Answers.com 17 Mar. 2006. http://www.answers.com/topic/for-a-song