Very good points.
However, in the "real" business world, whether you run Windows XP or
Linux or FreeBSD or any other esoteric OS, you will always have to have
an "expert" to help the users with the software.
Thus, it is incorrect to say that you will need hire an expert for
Linux, but no such need for Windows.
But it is correct that, at least at the present time, since most of the
existing "experts" are not well-versed in Linux, there will be some
training cost involved. This "extra" training cost should disappear
when Linux becomes more popular.