Penny wise, pound foolish. There are a few good posters on this article IMO who have a good idea of what businesses are weighing when making decision (slope987,razor512 to name two)
It seems a lot of posters have a hard time seperating the realities of business from personal computing. Business don't really care that a video card costs $600 to display 4 monitors (a fact many posters are missing also is that 4 monitors is probably not the end goal, 8+ probably is, no matter how you hash it Nvidia and ATI can only do two monitors per card so this card is superior in that sense). Yes, they could probably find a cheaper video card or other solution that would work.
In the end reliability and certification is FAR more important. If you have a glitch on a personal PC that takes 4 hours to fix and happens to be related to the particular hardware youa re using, it isn't a big deal. If you have the same glitch in a datacenter, trading desk, or other similar situation the loss can potentially run into the millions. In a case like this you want to be able to get on the phone and get the issue resolved quickly, and you definitely don't want a root cause investigation to point to the fact the hardware is not certified.
Are there high odds of this occurring? No, but then again the issue we had yesterday at work had probably less than .01% chance of occurring (network connectivity loss at the exact point a remote management process was setting permissions), but affected roughly 2000 people worldwide due to the process not getting its final instruction. Reliability is the number one priority when you run a business, as downtime will almost always cost you as much or more than you saved.