No, it varies with the bid amounts. How much you're willing to pay would determine how many impressions you would get. But generally, costs for different demographics will be a little different. There's a new loophole in Facbook ads though. Some ex-Facebook employee exposed it. The link is in my signature.
What is the summery of your comment? Isn't it?: Cost vary on advertiser's willing You are talking about minimum bid rate ya? But advertiser can increase rate for certain countries.
It depends on the campaign you run in each countries. You can set different bid prices for each campaign. But if you are running only single campaign then it is not possible to split the bid price for different geographical regions.