Yes, very cool idea. I really consider to build something similar... maybe start with 3-4 systems first.
but it would be possible to build a 24core box for less than 2500€
Intel Core 2 Quad Q6600
G0 95W, 4x 2.40GHz, boxed_______________________6x155,00€=_930,00€
Gigabyte GA-G33M-DS2R, G33 (dual PC2-6400U DDR2)_______________________6x_75,00€=_450,00€
A-DATA Vitesta DIMM Kit 4GB PC2-6400U CL5 (DDR2-800)____________________12x_55,00€=_660,00€
Samsung SpinPoint P120 200GB (SP2014N)________________________________6x_32,00€=_192,00€
FSP Fortron/Source FSP300-60GLC 300W ATX 2.0, 80mm fan • aktive PFC________6x_12,50€=__75,00€
Fan YS-Tech 80x80x25 Standard FD128025LB-N, 1600rpm, 40m³/h, 17dB(A)_____12x__5,00€=__60,00€
___________________________________________________________________________2367,00€
HELMER cabinet

______________________________________________________________25,00€
___________________________________________________________________________2392,00€
maybe a better PSU, 12cm fans and a better coolable case... but it should be possible for 2500€
