I think trying to put a value on what someone should charge for making quilt that we know nothing about -nor do we know anything about the skills of the maker - is about as sensible as trying to say what the weather will be like in an unknown location on an unknown date.
That said - for those that want/need to charge for making a quilt - go for it - with all the cautions that have been listed elsewhere.
For those that prefer to only do 'give-aways' - please don't knock those that can't afford to or don't want to.
As far as $/per hour - that is a tough one to put a value on - some people can get a lot more accomplished in an hour than others. Skill levels vary considerably. Where one is located also will affect what one can reasonably hope to get.