I can see your point but in one hand they are using their time and energy to provide us answers. I mean as a customer we also have the ability to evaluate whether we want to pay them or not, no?
Look at like consultants for companies and stuff charging 1000s of dollars a day. I do agree in some cases it's a bit much but then again it's their service there's no obligation to help people for free or cheap type thing. I've met some awesome people who have helped for free though and don't believe in charging for their abolities