What is the definition of 外省? In the following answer in 知乎, the respondent said the following to a question asking how much it costs to live in Paris:


  外省7-8万，巴黎10W+


I would like to know what 外省 means here. 省 means province so it is clear enough for me that 外省 at least doesn't express the metropolitan place like in Paris.

However, what kind of areas or districts 外省 mean? Is it a suburban or rural? If you relate it to Paris, does it point to somewhere except the central of Paris but in the il-de-france region, or outside of the il-de-france but still in Paris, or totally outside of the Paris?
外省(outside provinces / other provinces) refers to all provinces other than 本省(own province) - the province you are currently residing. In this case, 外省 means any province other than Île-de-France where Paris is located in.

Paris is a city, so "巴黎10W+" refers to the living cost in Paris only. The quote also mentioned cost outside of Île-de-France "外省7-8万" but did not mention the cost to live in Île-de-France itself. 

Either the writer presumed the cost to live in Île-de-France is the same as in Paris, or he thought Paris is a province.