I’ve known this shop do the same thing before and it grates with me. The term ‘reduced to clear’ is obviously intended to give the impression that the buyer is getting a bargain when they’re not. It might be argued that the word ‘reduced’ is not strictly a lie since the pack price has been reduced, but the product price hasn’t. Getting three cans of lager for £4.50 is the same as getting four cans for £6. So although it isn’t strictly a lie, it’s very close to one, close enough to be certainly dishonest.
No doubt this is another borderline case where the legal phrase caveat emptor applies, and it’s one more small example of why shoppers have to be so vigilant these days in order to avoid falling foul of the shady little tricks the commercial world tries to play on them.