That depends. The cost of your website depends on the complexity of the design, number of pages, custom programming requirements and sources for the content.
The important thing to keep in mind is the real question shouldn’t be “What does it cost?”, but you should be asking “What will be the impact to my bottom line?” .
So if you are trying to work within a tight budget, find a designer who understands how to optimize your site so the search engines will give it the best rankings. Otherwise, you may want to wait on building a website for your business because spending money on a cool looking website that isn’t optimized is a wasted investment.