Our center charges $40 for 25# of clay which includes bisque , glazes, glaze firing and use of the studio.
We do have some equation and charts based on size of piece you want to fire but fortunately no one does this very often. Take home clay costs $15 and those potters all have kilns at home. Only clay bought at the studio is allowed to be fired. Google search reveals various ways studios handled this matter. One charges $4.50/ lb.
I had this happen on a glaze firing,,,, the kiln sitter cone broke. I called Orton and they said to check each cone by holding with fingers and pull... not twist. The cone should not break. I had about 15 in a 50 piece box break. Not sure why... defect in cones or rough handling in shipping??? But with the test pull I feel more confident it won't happen again. I had some interesting glaze melts which didn't quite correct in the refiring and never to be replicated.
"Don't be afraid to be afraid". Not sure who said it but words to push you to new heights.
About liking pots later....some pots came out of the kiln not what I expected so I immediately gave them to a friend (she liked them). A year later or so I was at her house. I saw these lovely pots and asked where she got them. She said from you. I loved them...the glaze was quite nice and colorful. You just never know.