Designing a site is going to have a very different cost every time depending on many factors. The first thing to consider is the kind of coding that will be implemented. The graphics and the layout are secondary to the amount of dynamic code and features the site requires. Everything needs to be clearly laid out in order for a cost to be presented by the designer.
This is the main reason why that question cannot be answered easily. There are too many factors involved in this process and they all need to be considered before a decision is made.