Thank you all for the great information, I wasn't expecting so much depth but it helps me a lot.
One specific question I had was figuring out the cost of materials used in a project...
For example: Say I have a block of wood 1"x 1"x 12" that cost $50, and I cut a slab 1/8" thick to use for a project, how do I figure out what the cost of that material is?
25 percent figuring a 1/8 kerf if the slab is 1/8 x 1 x 12