Quite often when I start at a new client they ask me what are the benefits of TFS (Team Foundation Server), as they can not justify the cost, as it is very confusing (like may of Microsoft pricing structures)
I found this about "How much does Team Foundation Server REALLY cost vs SourceSafe?" by Eric Nelson, which is just what I have been looking for, as you can see the cost is not that much more than SourceSafe, and you gain huge benefits from TFS, as it is not just a Source Control, it's much much more.