Some comparative frame weights.
"Although a new TT frame had been under discussion for some time, Trek was able to fast-track the design this spring. "We looked at four key design parameters", explained Daubert. "One, aesthetics; we wanted the bike to look good. The look is evolved from the tube shapes of the Madone. Two, weight; we wanted the new time trial bike to be lighter. The previous model weighed in at about 1680 grams (without fork) but the new TTX is 230 grams (8oz) lighter. Three was stiffness; the new Madone derived top-tube shape has a more rigid contour that makes the TTX more stable and transmits more power. Last but not least was aerodynamics. This was the hardest parameter to deal with, as we were looking for big increments in the wind tunnel numbers, but it turned out that the older frame was already really fast." http://www.cyclingnews.com/road/2005/tour05/tech/?id=/tech/2005/features/tour05/lance_tour_tt_bike
"Our local Cervelo rep dropped by the Cyclingnews office with a P3 for us to drool over, and we took the opportunity to throw it on the scales. The bare frame weighs 1410 grams, which isn't stunning by general road frame standards, but is very light for a specialist time trial frame. The matching fork weighs 600g with an uncut steerer while the very aero special seat post comes in at 235g."