I use the materials cost x3 formula. 1x pays for my materials, 1x for my consumables, finishing supplies, and tools, and 1x pays for my time.
This isn't a foolproof formula, of course. There are adjustments based on the labor I put in, and the perceived value of the end result. I don't sell bowls, for example, because there is a lot of labor involved, and the blanks cost a lot. Most people aren't willing to pay $100+ for "some wooden bowl." I've also found that segmenting, in most cases, doesn't warrant as big of a price increase as the extra labor and materials would warrant.