cheap at half the price

After breakfast, Shirley and Gordon walked down the street to a shopping mall to look at fancy clothes and high priced jewelry. "Cheap at half the price," Gordon observed. Shirley smiled.

After he'd convinced you you'd only got one leg – the left – he'd sell you a gross of right-footed shoes. "Cheap at half the price! A real bargain." Afterwards, you'd feel you'd been done a favour to, and obligingly walk off with a limp.