The cost of retraining can also vary widely within a single organization, simply because not everyone will need to be retrained in the same ways. To restate the above example: if youre in an environment where most of the people use a heavily macro-driven set of Word documents, the bulk of your userswho just use Word and dont code for itwould not need to be retrained if you switched to OpenOffice.org. However, the few folks you had on staff to create those macros would need to be retrained on the new suite.
In the end, though, the only truly accurate and useful TCO study for comparing Windows to Linux is the one you conduct yourself. You can look to other TCO studies to get an idea of how to model one for your own organization and needs, but youll need to know your own environment intimately to get a real grasp of the cost. Whenever possible, look to another company whose work habits and needs match your own and learn about what they didyou may be surprised at how the costs added up or leveled out for them.
Sometimes you need to spend a lot of money now to save money in the future, and what looks like a bargain at first doesnt turn into a bargain later.