Chaim Yankel replaced all the windows in his house in Chelm. He had expensive, double-insulated energy efficient windows installed.
Twelve months later Chaim Yankel gets a call from the contractor, complaining that the work has been done for a year but he hasn’t paid yet.
Chaim Yankel replies, "Now don't try to pull a fast one on me. The salesman who sold me those told me that in one year they would pay for themselves"