I remember early on in my web development career to make sure you are selling a service not a product. You aern't building a website - you are providing a marketing service, requiring expert advice and a component of that service is building a website. As people have said, websites are easy - Wordpress + theme + hour of time and you are done.

Sell your knowledge of digital marketing - SEO, Adwords, etc in order to drive sales for your client, which is ultimately the reason they want a website in the first place.