I think the question is not well put and perhaps we should ask ourselves how much students can afford. When we see their debt, we realize that they are already paying too much.
In Quebec, funding is between 17% and 20%, and it is going down. Actually, the government has stopped funding universities. It even tried to increase student contributions. The question that should be asked is how much can we ask students to pay, given that they are already going into debt and putting off their life plans.