These are "workingmen's restaurants". You often get an appetizer bar (salads, pate, pickles), a set plate (maybe no choice or 2 choices), a dessert, and 50 cl of wine or cider. Very basic, but fun. We've been to one near St Malo, and tomorrow go to another near Quimper. Look for a restaurant advertising "Dejeuner formula 16E." Look also for the parking lot filled with white workingclass step-vans. And these are lunch-only places.
Yep, 16 Euros for all that.