This eight sided roof was custom covered with solid 16oz copper sheet metal for a Victorian style play house that we helped to build and transport for a local children's hospital charity auction.  It had about a 20/12 pitch roof, and is about 36" wide at the base.  We also made the copper ridge for the top of the roof sections, and a mini gutter for around the porch roof.  You cannot see it here, but I also fabricated a custom valley and some flashing for behind the turret, where it meets with the roofing. (see: www.dmrgutters.com/pg/prov.htm for more details)

If I were to build this for a paying client, the turret copper cover would cost about $750 for the 30+ square feet of copper needed to be fabricated to cover this turret roof.