I found this whitepaper and although it uses Redhat Enterprise Edition ($1200+) for calculating for the Scalix cost and don't use the Present Money Value concept for
comparing 2 expenses, it is a good reference document.
http://whitepapers.zdnet.com/download.a ... cid=290560
BTW, You may also notice from the document that the corporate versions of Scalix are not too much less expensive than Exchange. So if that is true, what other arguments do you use to convince an IT decision taker to choose Scalix. Taking in count that Blackberry solutions are easier/cheaper to setup on Exchange boxes.