Homebrew PCBs

I am in the process of making a cnc pcb engraver and it seems like 
the hard part is the designing.  I was thinking of offering a kit or 
the whole thing for sale or auction.  What I am building will also 
be capable of machining wood and plastic up to like an inch thick
(hopefully).  This would allow you to make custom stamps from bitmap 
images (great christmas gifts for women and kids).  I would not sell 
software with it, as I have found several free programs for doing 
what I would like to do.  I might include a cd with the free 
software on it but would need permission from the programmers 
first.  The engraver would be capable of working with like 14" by 
14".  This may be premature, as I am still in the design stage, 
But... My question is, what would be a reasonable price to pay for 
such a thing?  If it is not worth doing I don't want to make it 
easilly reproduced.  What do you think?  Would it be worth doing?  
Thanks for any input!

Ben Englund