I picked a model that would be pretty challenging (all curves) but not ridiculously complex. There are limits as to how delicate your details can be and still come through on the "printed" core - but adding details would be easy later on in the process. It is a great way to obtain the overall structure of a piece.
Even though it's dramatically less expensive than having a rapid prototype printed (3D print), it's still not terribly cheap. I got 40% off on my laser cutting and it still cost $115 for the service. You *could* cut out all of the pieces yourself, but I'm in favor of retaining all the sanity I can - lol. Once everything is added up, you could be looking at a few hundred dollars once you add in filler, primer, paint, sandpaper, glue, etc. The price will be dependent on the size and complexity of your project (you pay by the linear inch of cut for the laser cutting service as well as materials) and whether you decide to go for less expensive materials (paints, primers, etc).
Cardboard "core" sculpture
Body Filler (I used the Evercoat brand as it's the smoothest I found)
Plastic spatulas (some way to spread and mix the body filler)
Glue (I used yellow glue because it allows for some movement as you place layers of cardboard)
Weights (some way to clamp the layers as they dry)
A few pins (used to align the layers with each other)
Sandpaper (I didn't use very much, really - maybe a sheet of each - 80, 150, 220, 320, 600 grits)
Primer (a good quality FILLER primer - I used a catalyzed filler primer by Keystone - #8882)
Paint (if you want it - could be rattle can paint - or something more exotic)
Sureform or Rasps (used to shape the rough filler)
Misc (this is the catch-all category - tape, drop-cloths, etc)