plunder the tip
v. phr.— «Plundering the tip—to give away several free articles together with goods sold to create a feeling in the crowd that the house is full of bargains.» —“Jewelry Auctioneers’ Jargon Obtained From Auctioneers and Jewelers on 42nd Street and 14th Street” by Hatch in New York City Lexicon of Trade Jargon , 1938-39. (source: Double-Tongued Dictionary)