In the "low" season, staying in one of the best hotels in Cannes costs an average of 200-300 EUR per day. In May-September the price increases at least twice (300-1320 EUR).
In the "high" season for a room in a 4-star hotel in Cannes you will pay 160-250 EUR, in 3-star hotels you can stay for 100-200 EUR per day. The average price for a room in two-star hotels is 60-80 EUR, and hostels will give you a bed for 20-30 EUR.
It's quite difficult to come up with an average cost of living in Cannes. It depends on when you want to come to the city, what kind of accommodation you are going to rent, where you think to eat, whether you will visit paid beaches and so on. If it's important for you that your stay in Cannes is inexpensive, we inform you that it's possible to stay within 100 EUR for a couple of days.
The city has free beaches, and entrance to many attractions and events is free. So the money will mostly go on overnight stay in a camping or hostel (20-30 EUR) and food. Cheap food can be bought in shops or at one of the markets. In short, even on a tight budget, you can find prices that make living in Cannes quite comfortable.