Working out a price per job isn't really relevant. Because job prices vary, the cost per job ought to vary too. What you are really doing is comparing your turnover with your net profit. At the end of the year, you know your total income and your total expenses, you work out the percentage of expenses to total and that is the percentage each job costs you. i.e. job value £100, profit as a percentage of turnover 75%, job cost £25. Job value £10, same percentage, job cost £2.50