 This approach to advertising was driven by Sinclair 's reliance on mail @-@ order marketing . It came with a high up @-@ front cost in terms of purchasing space in publications but it had the advantage of ensuring that all sales were firm and pre @-@ paid . A big splash on launch produced a large influx of cash at the outset of a campaign , though it did also depend on the advertiser having enough product to satisfy the initial surge in demand . The advertisements served an additional purpose of priming the market for over @-@ the @-@ counter sales by " getting the story across " , as Clive Sinclair put it : " Not that big a proportion do buy on mail order , but they see the ads , and that helps to prepare them for buying when the item appears in the shops . " 
