Paris is expensive and not at the same time. What Paris is to France, are certain places in Paris to Paris as a whole.
Point: Certain areas in Paris more expensive than the others. Let’s start with 5 more important factors:
Accommodation: 1 room/Studio may range from 400€ to 1200€ depending on where you live (There are 5 zones in Ile -de-France, region of Paris. Most of the population lives in Zone 1–2–3. 1 being most expensive. Eiffel, Louvre are in Zone 1. Disneyland in Zone 5)
Food: Avg meal for for 1 person at a decent restaurant might cost 14–15€ in Zone 1, 10–12€ in zone 3–5
Clothes: Depends on Brands. Plenty of street shops, Malls in Paris (All zones) Usually Primarks are in Zone 2–3 where you can get clothes for everyone in your family for 100€. In Champs-Elysee, may be one glove for the same price.
Shopping: Same as above, for all other products. Most of the French (local) stores are in the Zone 1. Therefore considering on your budget you can shop for day to day or month basis. Avg groceries cost in Paris for a month can be 200–500€ depending upon individual requirements.
Travel: 75€ (2018) Travel Pass for all the zones, all the mediums included.
As per the Govt. of France, an international student or a tourist must have atleast 615€ in bank account for per month basis to apply for the visa. Usually Paris exceeds this, other cities do not.
I studied in Marseille, worked in Paris. My rent in Marseille for a 20 meter square room was 392€ while in Paris it was 885€ (zone 2). Travel pass in Marseille was 35€ in 2016, Paris 75€ 2018. Groceries 150€ in Marseille, 200+ in Paris.
So for a normal ordinary life in Paris, 800€ is fine, for lavish 1000€ is good, for rich 1500€.