*Ahhh*... the anectodal computer iliterate friend/family member, let's de-bust this. The core point is: linux on the desktop is only fine for the computer impaired and the admin/devs. The use case in-between for the power-user, the original PC use case is not addressed (or even understood). Why it works for your mom? Because you act as admin for her, installing the apps and your mother just uses browser, email and open office. She will not try to install software or games meaning this is more or less the workstation-server setup, the use-case unix was used for in the 70s. And I would argue, linux is still stucking in this limited workstation-server mindset, built around a powerful admin and stupid user. And has still not understood the "personal computing" revolution in 80/90s which empowered the users to simply install software from whatever source (shop, internet) themself by "double click" by having technically a stable and easy to address platform.
My parents install software on their own just fine. To them, it's as natural as installing any Windows application. Even more easily, actually, because a package manager does it all for them. And now even Windows 8 uses such a model with the Windows Store.
* Number of times I've had to "admin" Windows for them: at least seven or eight times. Three of those times was due to malware.
* Number of times I've had to "admin" Mint for them: other than the installation, zero. Not once. It's been almost three years now.
So in this case, the anecdote is not debunked by your statement which relied on a blind-faith presumption.
I should also point out that an OS's history has nothing to do with its presentation. Windows 2000-XP (and maybe Vista/7, though I'm less certain) came from the Windows NT line which, surprise, was intended for corporate workstations-and-servers. And yet that turned out to be completely irrelevant, especially when you consider that another OS which is supported -- Apple's -- is built on the same Unix/POSIX principles as Linux. And don't say "Oh but one is BSD, the other is Linux", because your statement about "workstations" and admins doing everything for the stupid users on the other side of campus, was a quality rooted in both OSes' histories.
I understand that, unlike BSD, the many, many distros of the Linux do things differently. There's not "One Single Linux Way", the way that BSD maintainers do things, but I don't agree that this is cause for as much confusion about Linux support as people choose to be confused about it. Go with what the usage statistics say for desktop users, and then only guarantee support for certain flavors of distros. There is a reason those are the most widely used, because free operating systems run within the rules of the invisible hand of the free market as much as commercial OSes do -- there are concrete reasons why those distros are the most popular. You can support the most widely-used format, and not worry about whether or not Slackware or Gentoo users will have trouble running it because you can label your release as being for those types of distros only.
According to Distro Watch, the three most widely-used distributions are all Debian based (Mint, Ubuntu, and of course Debian itself). So with the standards these three have in common for software packaging, there is a momentum that can be exploited.
So no, Linux support is not that expensive if you have someone knowledgeable about this in your company who can plan accordingly.