From Future

[edit] Cost

Rather than using brake cables and industrial control solenoids, how about using servos for model aircraft, aircraft control surface cables, and then a servo-control board to drive it?

Costs
  - 8x Servomotor = 8* $16         = $ 128
  - Servo control board            = $  50
  - Cables, epoxy, return-springs  = $  50
  - Material cost of 'hand'        = $  12
  - Material costs of 'arm'        = $  12
  - Webcam with optics             = $  43
                            Total: = $ 295

This is with Sept 2006 pricing.
N.B. Needs a PC and software to drive it.

I'd suggest you use a 3 fingered grip, not a 6 fingered one, since that cuts down on servos, and hence on cost per rig. It's also easier to control for the same reasons that a three legged stool is more stable than a four legged one. Note that there is no force feedback, i.e. no sense of touch, in the grip. It will all have to be done by visual feedback and that will certainly make the software more complex.