I would like to suggest two "quick and dirty" checks to make on your bids. While these methods are far from perfect - so simple, there are many things that might throw them off - I find them a useful check. If my quote differs by much, I will look closer at the job, and try to determine 'why?'.
Ball-park check #1: Triple the cost of the materials. This ought to be about your price. Can be thrown off by the use of specified products, or jobs that have little in the way of materials.
Ball-Park check #2: Triple the base pay of the guy who will do the work. For example, if it will take your $20/hr guy an hour ... 3x 20= $60. Your price ought to be more than this figure. This method is useful in deciding whether to rent equipment to speed up a job.
