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					Originally Posted by  HarryT
					 
				 
				It forbids discounting by the retailer; it does not mean that everyone has to sell it at the same price; the publisher is entirely free to set different prices at different retailers. 
			
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 In the US, setting different prices for different retailers on any basis other than volume would almost certainly be a violation of the Robinson-Patman Act.
Even if it was strictly legal, retailers would unleash the legal hounds, pull titles and otherwise punish the publishers.
Penguin already has its own store.  I haven't checked it carefully, but I seriously doubt they are undercutting the retailers.
UK prices could be (legally) different from US prices for many reasons including VAT, sales tax, currency fluctuations, demand &c.