Earlier quoted context omitted.
If anyone could have built it, why didn't anyone build it until now?
You have projects like http://beagleboard.org/ (beagle xm $150 and $89 beagle bone), and http://leaflabs.com/devices/ ($45 maple), which are all ARM based devices, that have been around for a while. I just don't understand how these guys got it so cheap, which is why it seems like they just optimized the bom to get it to where it is. I'll hand it to them though, that is an impressive feat.
Also, it's like saying that DarkShikari et al. "just optimized the code" to make x264 the best easily-available encoder of H.264 on the planet.
Finally, the Raspberry Pi is tremendously more powerful than the Maple.