It depends on the development time. Many companies work on a price per page but this can be misleading because certain designs may have very small pages with little content so they should be cheaper. A good information hierarchy should lead the user quickly by good navigation to the information they want, cramming as much content as possible onto pages to keep the page count and cost low is a bad approach.
Our solutions are all priced individually and typically start at £300 - £500 for a 5 - 10 page site in a one-off design. Of course if existing branding is in place this is adopted and taken into account in prices.