My guess is 5%, 10% tops. I think for ready-made printers the price will have to come down to the $200US range before it starts attracting the casual user.

(I would not have become involved with 3D printing if it were not for the RepRap. I was in love with Makerbot, but it was going to take some smooth talking to get my wife onboard for $1000. I was able to source the RepRap Prusa myself "under the radar". Now my wife is all-in. But a Makerbot would still be a bit of a sell.)