I think that you will find most charter airlines charge extra for exit rows, they justify the surcharge on the basis that they offer extra leg room.
I have no problem with airlines charging for the exit rows but I do think that the regulations on who can sit in the exits should be beefed up and more strictly enforced. I have seen people (both male and female) sitting in the exit rows that, in my opinion, are incapable of opening the exit doors easily and therefore putting the lives of others in jeopardy.
I have only opened an overwing exit once and found it far more strenuous than i expected.
And before anyone asks, i am 5'10", 90Kgs and am used to opening cabin doors.