Sorry that it takes me so long to get back to your question. I built one similar to the one in Daniel Wing/Alan Scott's book, The Bread Builders: Hearth Loaves and Masonry Ovens. It would be difficult to estimate what it cost me as much of the supplies I used came with little or no cost from scrounging up materials left over from jobs and such. The parts list on page 168 of their book could be helpful in estimating a 32"X36" oven. That is roughly the size I built. Local materials make the size nominal at best. I can get 16 loaves of bread into it at a time. I can do 3 pizza's at a time if I can prep them fast enough (with helpers). Otherwise it is one at a time. Good luck.
Like Bill P, I built a 32x36 Alan Scott design oven. granted I tend to over build and the basic structure that supports the oven will last forever - I think I have about $1500 into the oven so far. That being said, I have not completed covering the outside in stone (vs grey block) nor put a roof over the oven itself. i dont plan to use stucco as it really doesnt go with the motif here in Atlanta..
I do have a pats list (to date) if interested..