If anyone has back issues of Screenprinting Magazine from around 1991 (+-3 yrs.) there was a worksheet in there taking into account costs for inks, screens, reclamation, solvents, shirt costs, design process, markup, electric, insurance, rent, and much more. Practically everything you could imagine.
If anyone can find it and scan it (2 pages, I think.), I'll make a PDF Form of it to automatically calculate job costs for you and post a link to it.
Richard