Because food cost percentages are lower doesn't mean that other costs aren't higher. Plus a smart Chef will offset high end ingredients with lower end ingredients. The food costs percentage for that dish was very low. I agree with all of your points, and if true then I need to question the restaurant's concept. I would think that few patrons will go to an upscale quality restaurant that specializes in foie gras and truffles to eat cod.
Proper recipes are vital as is the updating.
Yield factors are important or you get the wrong idea of your actual purchase price. Francois, just from general experience I don't think that an upscale operation serving the kinds of quality products you do can pull off such a low food cost.