Why Free Software's Long Run TCO must be lower Brendan Scott 15 July 2002
http://www.members.optushome.com.au/brendanscott/papers/freesoftwaretco15070...
Haven't fully read the paper yet, thus I don't know how good it is. Still I've found paragraphs I liked already:
Source code sharing arrangements where the source code for proprietary software is made available but not on a free software basis, are dangerous for users because of the viral nature of proprietary software.
8. Strategic implications for purchasers.
(a) The short term costs of proprietary systems may be lower than those of free software systems. However, free software systems hold the advantage over the long term;
[..]
We note that these conclusions are independent of the fact or amount of any license fees charged in relation to the proprietary software.
Note that this seems to be an argumentation focussing on the monentary aspect of software. There is also an ethical aspect to Free Software which is important to companies and people on a higher strategic level.