Achellin,
Not being rude, but either you didn't read the posts, or somehow you just don't understand them.
The costs associated that make Linux more expensive are not the direct OS costs. Also, the training for the IT staff will vary per organization. Many people in IT, particularly in larger organizations, have to focus on one specialized area. The same guys who help with "desktop support" will NOT be the same guys handling the Linux-based or Unix-based or Windows-based servers.
Also, you're not thinking straight on drivers. Sure, any modern OS will "do it by itself" to some extent. However, there are just too many hardware configurations to be able to handle it all. Now, on the coporate end, it could be argued that they'd use much the same or similar hardware, so they may be in an easier situation with hardware drivers in that sense.
User training - if you don't train the day to day users of the system, then you're going to be in for some real pain as a business, and more than likely fail as a business. If the users don't know how to USE the system, then it'll cost more than ANY OS would cost.
Programming - the Programmers are not Linux administrators, sysadmins, or the like. In large corporations, oftentimes, the programmers write programs with the tools available for the systems available in the company. Most of the time, they do NOT program for cross-OS support and the like. It'd be better if they did, but by not worrying about that, they can get more "bang for the buck" by getting the programmers to "get it done" for what the company is using now, or is planning to use in the near future.
In other words, if the OS cost $300 or $400, even per system (which it doesn't - and $200? really? Not when the corporation gets a quantity discount type plan that most get..), it would STILL be cheaper to stick with Windows.
Besides that, most large businesses/corporations will primarily use the same Office software and other apps they've been using. Why? Again, same reasons, just for the applications instead of the app - custom programming, training, etc.
What do people use in Offices? Primarily Microsoft Office, which is available on MS Windows and on Mac OS. They also use Adobe products, in particular Adobe Acrobat.
Sure, you could sue Wine to run some Windows apps, but then you're just adding more possible headaches that no one in the corporate world needs or wants.
It really boils down to this simple fact:
Businesses are in business to make money. If it makes sense (on a large scale, not individual likes) to the business, that it will be help make money rather than just spend money, then that is what the business will choose. That's not to say that businesses don't make mistakes.
Think of it this way: the vast majority of businesses and home users use Windows-based computers. So, if you're a business just starting out, and you go with Linux or even Mac OS, you've got to pay the costs for additional training for anyone you hire, as compared to Windows. With a Windows-based system, all you gotta teach is the specific apps you use. The basic Windows stuff (currently) is known or well adapted to by pretty much anyone.
I do like Linux, myself, but I cannot honestly see a really truly good scenerio for a large organization for all the many reasons already listed by various individuals in this thread.
At tek-tips, it's not about being "fan boys" of a particular manufacturer or product. Rather, it's about getting the job done - whatever it is, whatever it takes. The best answer wins, I'd say, is the main desire of most folks here. It's definitely a part of the idea of being a "professional" forum.