OP,
For what to charge...that varies. Certainly, you want to look at comparison stuff when it comes to materials because you want to charge differently for different materials. Now the value you place on the art will always be relative. You certainly want to charge to recoupe cost and make some money. You may have to experiment. I think the framed prices would vary depending on materials. How did your color copies turn out? Did you use cmyk palette in carrara or convert it in another program later? I am curious about commercial printing from carrara, since I would like to do this at some point. How long a print last and ages I would think would be important when talking about framed art tho.

No need to think outside the box....
    Just make it invisible.