How much should you charge to create and maintain a website using only html?

Only HTML? No CSS? No images? No server-side programs?

I think you shouldn't charge very much...

I'm sorry, yes there would be CSS and images.

Even if you mean the hourly rate it still depends on the amount of work involved.

If it can be automated by a skilled professional, the time required will decrease, at the same time the hourly rate may increase to reflect such a professional's higher competence.

Quality work usually costs more as well.

final cost very often depends on who's the actual customer..

Try to find out what your competitors are getting for the same type of work.
You should also ask for the same amount because lowering your amount is not going to give you better/more project but you will get extra problems and worries.