Make sure you count the home page!
In fact, if you will want flash, very complex art, or what have you, you may wish
to count it 2 or 3 times.
You may have a bunch of short, template pages. Such as, portfolio pages that show a larger image and a small amount of text, location pages, product description pop ups, etc. These might be counted as half pages or maybe 4 to 1. Depending on how much work is to be done.
Long technical pages, or pages with long tables or complicated layout, count twice. Various upper level pages such as the product or area overview pages, that might require art and tight layout, might be considered as 2 or 3 pages.