I believe the cornrow braids are $2 apiece, and loose braids are $1 a piece. The cornrows can either go the length of the head, or stop at about the place that you would put a standard headband. The second option is called "headband" or "crown" style. When you book, they'll ask you which kind you want.
Some people have said that their child had a lot of pain with the braiding (they do pull it tight), or that their child had a lot of hair breakage (seems to be worse with fine hair). My DD did say that they pulled, but she didn't cry or complain. We left them in about 2-3 weeks, and she didn't have much more hair come out than would normally be there in a brushing.
If you do this, TAKE SUNSCREEN for the child's scalp. I highly recommend the coppertone sport spray, because it it easy to apply to the parts. And think about what color beads you want. If your child has a beautiful red gown for formal night, you wouldn't want her to have purple and pink beads in her hair!