Imagine the texter/copywriter and the designer in the advertising agency of the discounter have the same "problem" like Jim Carrey in the movie "Liar Liar" – they can't lie anymore...
My idea is a parodistic approach. It's like the "real " discounter campaign is hijacked...
English Translation for the Lidl example: Claim in the real campaign "Lidl lohnt sich." = "Lidl it's worth it" The hijacked version "Lidl lohnt nicht." = Lidl it's not worth it".