Exploding or Squash books

Made these at school for the kids in our class. I think we might make more to sell at our next festival at school. These are made using the construction paper we had in the class. I will actually use cardstock to make the ones to sell. What do you think a good price will be? These are 8x8 squares. The purple is using 9 sheets, the other 4 are using 4 sheets. I think I will make most at 5 sheets. They just open better with the 5. What do you think? I didn't take great pics, so hopefully you get the idea of what they are. They are not 100% completed.