Different drivers and good support (directly from AMD/NVidia). The drivers allow better image quality and acceleration in "professional" programs like CAD programs (and many others). Hardware wise some have a larger framebuffer/memory and are often the best of the chips (which equals higher stability and lower temps/power). A lot of the cost is the support.
No, to people who are not in the business (working for a company) it does not and should not.
Think of it this way. To you or me, if we need support or help we do our own troubleshooting, calling around, RMAs. It takes a lot of time, but we see it as saving money as we did it ourselves.
Now to the company. If you the employee has to troubleshoot or argue with poor tech support for hours or days, your company has just paid you thousands of dollars to fix that card. So to them they might as well paid the cost upfront.
Additionally going along with the "time is money" theme, for us non-professionals it is better to wait or deal with buggy cards than to spend $2000+ on a GPU. In a company this GPU might be the workhorse of an employee that gets paid $120,000+ a year. So if the slowdowns or glitches caused by a non-pro card decrease his/her productivity by by even 5-10%, the pro card would easily pay for itself.
I'v often pondered obtaining a cheaper pcieX1 nvidia quatro for my meger 3d rendering tasks i may run in to. knowing full well that cheap quatro is going to be slow as beans in comparison to its monstrously expensive more effective models. but just for that instance i might want a higher quality render.. even if it takes weeks.. that pcieX1 slots been a virgen for much too long.
Well, that is the hard part - telling where the costs of a pro card balance the benefits. I know for the CAD programs I use and the models I make I am more CPU bound than GPU bound. Additionally, the final renders are done on the CPU in the program I use, so the quality is the same regardless of GPU. For your specific case you'd probably need to find a forum with people who use that program and see what their experiences are.