A week In Nice next week

May-August plane tickets will cost about £100 each. Sept-April plane tickets will be about £200 each.

Paris is very expensive, a run of the mill cheap hotel will be at least £100 a night. Plus food, attractions, taxis, etc. And the exchange rate sucks, a soda that costs you 1 in the UK will cost you about 2.50 in Paris, doesn't seem like much but multiply that by 30 and it's a lot. 
So summer- about 500 winter 100. Its a dump anyway so stay somewhere else like Croatia.