Hi there buddy, The pricing with the demo frames will be the same because Specialized feel that, that is a good selling price for their frames compared to other DH frames on the market. What I will say if you are interested in the demo 8 frame, go for the new one for a number of reasons.
A) The rear triangle has been slammed, so basically what that means is you get more traction from the rear wheel.
B) Even though you will have a slammed rear end, the stand over height will not be effected the BB height.
C) Linkage on and around the swing arms are under less strain and pressure, especially if you need to have a large size frame.
I hope this helps
Robski