Originally Posted by swamp2
For the sake of argument if they want to save 300 lb with CF that will take about 100 lbs of CF replacing 400 lb steel (super coarse "back of the envelope" estimate here). That will then cost just in materials at least $1000, not to mention higher tooling (fixed) and much higher labor costs (variable). I'd estimate the total cost (not price, cost) to save 300lb at about $1200. That must be increased further by their desired profit margin. It may not sound like a lot in a $60k car, but you would be amazed at what large automotive OEMs will do to save a few pennies on simple things like fasteners. $1200 is a HUGE expense.
With no particular fact-based argument to offer up to counter this point, swamp, my gut feeling is that your figure is off by a wide margin on the low side.
Also, regarding estimates, I saw your disclaimer and realize you were just throwing out numbers. That being said, if we wanted to get closer to real figures I would think that it would be pretty safe to start with the premise that there will be a higher cost per pound saved as weight tends toward zero. We can even put an asymptote at around 2000 lbs or so. I.e. it would cost an infinite amount of money to build a 2000 lb M3 (read: impossible).
Edit: You know what, I guess I didn't appreciate the fact that you were talking about material costs only. So disregard my statements as a counterpoint. However, they do make for a reasonable secondary supporting argument. Furthermore, I will suggest that material costs are among the least significant considerations. Though to be perfectly honest, I really have no idea what drives costs of carbon fiber. I suppose I should hit the search engines and see if I can find some information on it because you have piqued my interest.