When it comes to the high-priced website developers, they are going to have a reputation to back them. They are going to have a portfolio of professional websites they have created that are going to speak for their work. High-priced website designers are going to have people who could vouch for them as well as have a very strong web presence. This is the reason why they are going to be priced so expensively, because what you are really paying for is a degree of certainty, not necessarily superior quality.
CMS helps to separate design of web site from its content. It means designer develops a web site and gives it to its owner or manager who can fill a certain design with different content. If necessary the content of web site, its images and graphics can be easily edited without intervention into design of web site. All changes become visible as soon as you make them. (Don‘t forget to reload page after making changes). Even if you are not an expert of HTML coding, you can easily manage the content of your web site yourself.