Good analogy. But for a client who wants a simple web site, they will try to build their own as a cheaper alternative. As these web builders become more sophisticated, they will take a greater share of potential customers. How much complexity does an independant business web site need? A list of services, prices and contact details. You can get even get e-commerce packages and online catalogues.
I agree that for a high end web site, the client will require specific customisation not possible in a web builder. Plus they will have the budget to go pro.
Actually, i've just seen the prices for 1&1, it's £40 a month, not as cheap as I thought!