Yeah, it's rather slow, but consider the fact the 300 GB of space is required to host it, that would be rather expensive if you would also want it to be fast, especially for a "hobby" project. They prolly host it themselves.
Anyway, imagine the cost of having the SOASC-machine recording non-stop for 4 months! All that equipment and power costs!
Look also closely at the setup...note the CPU fans above the C64 mainboards (especially above the SID chips

) and also attached to the C64 power supplies.

Cool!
http://www.6581-8580.com/pictures/soasc=_overview.jpg