The initial costs of the R & D for next generation platforms were paid off by the AGP models and thus any card that comes out now will result in production costs. This is why a 400$ part 8 months ago runs for 250$ now. Selling x, y, z at 400$ recooped expenditures and now BrandNew Card 2006 has minimal money spent in advancement R & D so it takes the 400$ spot and the old card can take the midrange spot.
AGP happens to be a redheaded stepchild... they now need AGP bridges that require an extra 8-13 dollar part. Why they cost 30-40 dollars more usually is a matter of price gouging. In the next year they will increase by supply vs demmand.