Join Date: Aug 2005
Location: Rocket City, No'ala
Bikes: 2014 Trek Domane 5.2, 1985 Pinarello Trevisio, 1991 Colnago Master, '06 Bianchi San Jose, 1987 Moulton Fuso, 1990 Gardin Shred, '82 John Howard(Dave Tesch)
One way is to do price checks on all these items as though you were building your own bike. That would give you a rough idea but would assume a bike manufacturer is paying the same profit percentage on each item he(the manufacturer) buys to assemble his bike. I very much doubt that to be the case as some items are more easily manufactured than others and some items will have more pricing competition. These variations may/may not be reflected in the retail prices of these items.
You've left off quite a bit that also goes into the price of building a bike: overhead (labor, insurance, taxes, utilities, rent, advertising, marketing, shipping, profit, capital expenses, misc. expenses)
Another way to get help is to go to the source. On the Single-Speed/Fixed Gear forum there's a poster named Kogswell who actually makes/sells some cool bikes. I believe there are some other bike builders that ocassionally post also but you may just go to their websites and get their e-mail addresses. Don't ask for real numbers but they may be willing to give you the percentages you need.
While component pricing won't change, frame materials and methods of frame construction greatly affect the price of the frame which would then change the percentages. TIG welded aluminum frame will be cheaper than a silver brazed steel frame or a steel frame with investment cast lugs.