The formula is - Material+labor+overhead+profit=job cost.
You need to figure what your mix is going to cost,(what materials are going in to the mix and how many Sq' is this going to give you per bag, or cu.yard) plus any paper, lath, screws, and any other materials you are going to buy for the project.
How many guys will be doing the job, are they paid hourly or piece work? how much is workmans comp and insurance? how many Sq' can they get done a day? how long is it going to take to do the things that come up unexpectedly? If you're doing the job yourself, how many Sq' can you do in a day, and how much do you want to make per day?
Overhead - How many people, if any, are employed in your office, how much is office rent and utilities, gas for you and anyone else to get to the job? gas for equipment, equipment payments? How much is licence, bond, and insurance? - These costs will vary from state to state, city to city, contractor to contractor.
Profit -How much can you get away with making? Usually contractors will add another 10% - 50%, on top of the labor, materials, and overhead, depending on the size of, and how complicated the job, how long it will take, how long it will take to get paid, the economy, the number of contractors bidding against you, and how much you think you can get.
Estimating - When you're all done figuring out those things, you can divide your cost by the number of sq' on your job for a per sq' price. Just throwing out a sq' price at someone you are bidding a job to is dangerous. bid per job, not per sq'. conditions will be different from job to job, the style of the stone may take more or less labor, and one job may require a thicker or thinner carving mix, which will affect your material cost. Most estimators would make their own Excell spreadsheet, while figuring out the answers to these questions and typing in a formula for them.
Thats right , Im on it as I write .. creating the excell formula and adding in my formulas.
Thanks for the insight and I knew I was head in the right direction.