Customization – If you want a high end website with customized component on each page then you have to take professional service for design and programming.
Functionality – Interactive website design can either be inexpensive, thanks to modern tools and competition in web design market, or it can be extremely costly. The cost depends on the functionality you want in your site. If the site has complex custom functionality, like e-commerce, image galleries, sign-up forms, social media integration, mobile versions, etc., then that will also drive up the costs.
Content – If the site requires a lot of pages with original content like articles, landing pages, charts, graphs, and original photos, etc then it will need more copy writing and I turn incur most cost. Copy writing ties with search engine optimization to create copy that contains the right keywords and compels your visitors to take action. Free or paid CMS can be placed to edit information on your website without having to edit any of the code or mess with any of the files you already have in place.