I believe this type of thing is called a "loss-leader""loss-leader" - supermarkets use the tactic to draw consumers in on the promise of a few of their product lines being cheap - knowing that in the course of their shopping - customers will probably buy other goods at higher prices. Another description is that of "upselling"which"upselling"which is another tactic used by online retailers who tempt buyers with a small purchase and then - at the point of ordering - try to sell additional items which are usually higher in price.