An effective website is 90% marketing and 10% website design. A lot of people come into our office and ask: "Why does a website cost, 5, 10, 15K when they've had previous websites that were done for $2,000 or less.
The question I always have for them is "How well is that website performing for your business?" The difference between a marketer and a website designer building your website is a marketer is going to take the time to understand what your business is about, what your customer wants and what your competition is doing whereas a website designer will take the copy that you give them and slap it together with some programming and present a website that functions and might look great but doesn't have the marketing style that you need to appeal to the customer that you're talking to.
When you're marketing to your customers, it's important to understand how to market to them. What this really means is, what kind of messaging will your customer respond to; what kind of imagery and call-to-actions will they respond to; what techniques and strategy is going into your website to get the right people using search engines to find you?
That is a small list of the things a marketer will look at to show you some of the differences between a marketer and a website designer.
The next time you're interviewing a website designer, ask them what their experience is with marketing and what kind of success their past projects have had before you make a decision on how to have your website made. You will then have a good understanding of what you are getting for your marketing dollars, and hopefully a reasonable expectation of what to expect in terms of return on investment.