I think you're being told that if you're not willing to pay sky-high prices, you shouldn't go to Switzerland.

In fact, McD's does not seem to be a good value in Zurich.

If you were to search (using Google, for example) for "budget eating in Zurich" you would find lots of articles and blog posts. Almost all of them mention carry-out from supermarkets, and some suggest that Aldi or Lidl offers better value than Coop or Migros; most mention sausage stands on the street, especially Vorderer Sternen. Several mention cafés in department stores, especially Manor, at midday.

One out-of-the-way suggestion, and I mean literally out of the way of most travelers, is the university Mensa. There are multiple locations, but those at UZH Zentrum are not too far out of the way, east of Seilergraben. Locations with maps, hours, and menus are online, in German.