Website build costs can increase considerably depending on what you require. Any notion of online processing of details, shopping trolleys, selling online, basically anything above flat pages with images and text you will be hitting the thousands mark.
A more advanced site, requires more specialist software development skills, and leaves the realm of 'web design/brochure-like sites'
So as stated above, more detailed requirements of what you actually see the site doing are needed for any sort of proper ballpark quote I'm afraid