Many clients have no idea what they should be paying for a Web site. They will get a huge spectrum of quotations from companies and individuals of many different levels of competence and won't really know what is the 'going rate', if indeed there is such a thing. If you can show them exactly what they will be getting for their money - in terms of end results - they will be more confident about hiring you and paying what you ask - provided, of course, they can afford it, which is another story!
I can't give any guidelines about specific amounts or even hourly rates, there are too many variables. You should know what you need to earn.
In the end, it is a design job. They are paying for design, both functional and aesthetic, not for HTML files. That design job requires a high degree of talent and you also have to own the correct tools - hardware and software. You might have a single Mac or PC, or a bank of different computers and monitors all needing different software licenses - that's expensive.
You could work from your bedroom or from a plush office with a receptionist and conference room. All these factors are going to have an influence on how much you can credibly charge.