Source: wikipedia.org
The Quadro series of video cards by NVIDIA Corporation is a set of AGP and PCI Express video cards targeted at the professional workstation market. These cards are essentially identical to the company's popular consumer GeForce cards. Unlike those cards, however, the Quadro cards are certified by companies such as Autodesk for use with their workstation applications in fields such as computer-aided design and computer-aided engineering. The Quadro line relatively closely tracks the GeForce line, though some cards, such as the Quadro MVS series, are tuned specifically for 2D applications and have no direct GeForce counterpart. In general, a Quadro card has the same designation as its GeForce counterpart; for instance, a Quadro4 is equivalent to a GeForce 4 Ti series card. This similarity means that GeForce drivers, which are newer and more advanced than the Quadro drivers, can be used to drive Quadro cards. Doing so voids the card's certifications but often results in higher performance and better features.
The certification processes to which the Quadro cards are subject, combined with their targeting at the professional workstation market, make them significantly more expensive than GeForce cards.
Guess it explains why these cards cost more. I also thought that the high end cards have a lower probability of making an error than the gamer cards - at the h/w level. Might or might not be true. Anyone have info on this? Not talking about s/w drivers.