I usually take the time into more of a consideration than the materials cost. Another method is to look at what the cost would be to print the part via a commercial 3D printing company/service, and determine if you want to come in under, at, or over that, as a means of checking your baseline price you come up with vs what is available from something like shapeways, stratasys, protolabs, et cetera For some people, they don't attach any value to their time. For others, time is the critical factor and vastly outpaces the materials costs. In my machine shop, my base rate is $90/hr. That's spindle time, not clock time. So if a part has a cycle time of 90 minutes, that is $135 + materials + finishing / post processing time. Everyone has their own ways of determining what their time and efforts are worth. There is no one "right" answer. You have to determine what works for YOU and charge appropriately. Then, you can see if you are competitive. I have also farmed out work that I couldn't do MYSELF at an economical scale, but can sub-contract out to someone with something which is better suited to the manufacturing method than what I have, and still deliver the product to my customer at a price they are happy with and I still earn income as well as who I sub-contracted out that part of the production.