FYI, there's a rumor going around that in May, Sony will bring back the 40GB PS3 at $299!
Looking back at a couple old articles, this actually sound quite possible.
Currently the $399 80GB PS3 has a 65nm Cell and 65nm RSX GPU. These articles show both of these parts going down to 45nm early to mid 2009.
http://www.obsessable.com/news/2009/02/05/playstation-3-to-get-45nm-chips-by-middle-of-2009/
http://ps3.qj.net/Toshiba-to-manufacture-PS3-s-45nm-RSX-chips-by-2009-65nm-chips-by-next-month/pg/49/aid/108503
Moving to 45nm parts means they are cheaper to manufacture and produce less heat(which means they can slim down the cooling system further saving money)
So: 65nm Cell > 45nm = cheaper
65nm RSX > 45nm = cheaper
slim cooling system = cheaper
80GB HDD > 40GB = cheaper
As the Cell and RSX are 2 of the most expensive parts in the PS3, it's seems very reasonable that these 4 factors could shave $100 off manufacturing costs:)
We shall see.
