When I see charities that employ people in expensive locations I don't feel like my money is actually having any impact. Remember the 80000 hours advice? Make a boatload of money and spend it on charity? That doesn't work when working an additional 40 hours of overtime a week results in someone else getting a 20 hour per week position at a charity because they earn twice as much as you. Why not just do the 20 hours yourself at that point? Save money for a year. Be a volunteer for 6 months. Except people won't do that. So nothing gets done in the end and since the charity probably wastes the money anyway you don't even have to feel bad.