Well, I dont usually do to many fiberglass boxes, just because there isnt a demand for them where I live, but I usually use a three tier systme....I usually charge 50 dollars for Materials (depending on project size) 100 for labor (also depending on size) 20 extra to carpet, 30 more for vinyl, and an extra 50-75 for paint, (depending on the grade of paint that I use, and the number of clear coats.)