It's just a pure marketing ploy by Migros; it doesn't mean that everything that is advertised is true... Unfortunately, many people still believe the advertising/marketing etc. and Migros takes advantage of this or Migros profits from it (not only Migros, but also many other companies/companies that advertise); also, many people are lazy about switching (see e.g. health insurance) and are creatures of habit etc. Anyone who regularly watches e.g. Kassensturz, looks at online tests, informs themselves in other ways (e.g. 20 Minunten: https://www.20min.ch/story/lidl-und-aldi-duellieren-sich-mit-ffp2-tiefstpreisen-492439495897; https://www.handelszeitung.ch/unternehmen/so-setzen-aldi-und-lidl-die-migros-unter-druck; https://www.nau.ch/news/wirtschaft/so-haben-lidl-und-aldi-den-schweizer-detailhandel-aufgemischt-65496532; just google it, there are many such articles online) or regularly/often go shopping in discount stores (Lidl/Aldi) have long noticed that Lidl/Aldi are outstripping Migros. In my opinion, Migros no longer has the best price/performance ratio, perhaps for a few products (e.g. products that are not yet available in the discounter's regular range or similar); for me, Lidl/Aldi are the clear price/performance winners in many respects and with regard to many products. And the quality of Lidl/Aldi products is also much better in some cases than at Migros (e.g. fruit, vegetables, etc.).