A 4,000 Euro supercomputer?

I’ve heard of a lot of unique ways for consumer electronics to be transformed into new creations.  But this has to be the first time I’ve ever heard of a consumer component based “supercomputer”.   Apparently a group of tomography researchers have chained four nVidia Geforce 9800 GX2’s in one computer along with 8GB of RAM, 750GB of hard drive space, and an AMD Phenom 9850 quad-core cpu.   What’s crazy about this is that the four Geforce cards represent 4GB of memory and 8 GPUs.   The above link is to engadget which has the story and the video made by the researchers explaining what they do and why they created the supercomputer.   The highlight of the video is undoubtedly when the narrator has to kick someone off the computer who’s playing a computer game.   Perhaps a better question after watching all of this is, why hasn’t some game computer builder made this before?