the 4.0 is nice because there simply isn't any other 40mm rim out there that's as light as what soul uses.

now the 3.0 uses a 30mm rim that's probably the same thing as the kinlin XR-300 and otherwise uses what appear to be either aerolite/CX-ray spokes or DT aero spokes.
basically, they're not that different from what you can build from parts available off the market.