Areas of town such as the Invalides, Eiffel Tower and Palasie de Chaillot are more serious about dining which is reflected by high prices. The eating diversity of Paris is great. The regional dishes are well-preserved at many of the bistros some of which are elegant because the chefs have worked at the named restaurants and have now opened their own business. Restaurant dress is as you please, within reason, unless dinning at a three-star restaurant which is rather formal. Table reservations are recommended to avoid a wait.
Prices can range from very economical to very pricey.
You can find lunch at a cafe for F80, but a good bistro or restaurant will range F200-F250 for lunch including wine.