waterbed effect
n.— «The larger chains can extract more favourable conditions from suppliers than other types of retailer can. They are able to do this because of their market shares and integrated supply chains. The result of these practices can be what is known as the “waterbed effect,” when suppliers raise prices for other buyers (including independent shops) as a knock-on effect.» —“Tesco could be built in Farnworth” by Amanda Smith Bolton News (Lancashire, United Kingdom) Mar. 31, 2008. (source: Double-Tongued Dictionary)