I came across this handy SharePoint price calculator from Bamboo:
http://community.bamboosolutions.com/blogs/sharepoint-price-calculator/default.aspx

The tool gives you an rough idea of which licenses are required for your MOSS deployment and how much they will cost. Note that costs may vary depending on the license contract that is in place. Please check with our dutch licensing site or call +31-20-5001500 for more information.

-Andre