They have much better drive support and are targeted at corporate work stations that are running programs that cost 2k-10k per seat, if you just dropped 20k on software for a computer you definitely want to be able to blast through it reliably and quickly. The pro cards like the quadros have their driver optimization dedicated to work station applications rather than games so they perform worse in games, and better in work station apps even though hardware wise they are very similar or in some cases identical to their gaming counter parts.
Also consider that it costs just as much for the design and manufacturing setup as it does for the gaming cards, but far far fewer are sold. There are a lot more costs per card sold than with gaming cards.
In years past, the Quadros were simply PCB-cut (a few connections cut on a resistor pack to identify the card uniquely as a Quadro) commerial gaming cards miraculously flashed/recognized as Quadros....
Those that think the Quadros have some special powerhouse GPUs under the hood will likely be disappointed to know that in reality they are paying 3x as much for a GTX460 equivalent....
In certain situations they can tweak a custom driver for you if you having some rendering issues with whatever program you are using. That takes time and costs money to come up with a custom solution for a single or small group of individuals.
It also generally cost a little more money to manufacture a professional card since less of them are manufacture. The smaller the production batch, the higher the price just to break even. Then add in the custom driver support.
I wonder if you could google a benchmark comparison. One thing to consider for a professional stand point. If getting a slower card causes you to wait more, that costs you time and money. If you are doing Autocad as a hobby, that's different.