Sony has always been and still is losing money on every PS3 sold so you can see why they did not implement an N card, even today an N card (for a laptop) cost approx. 2x the price of a G card

plus a lot of consumers are yet to move to N
BELKIN F5D8073UK N 802.11n - £29.90 (Notebook Network Card)
BELKIN F5D7010UK G 802.11g - £15.54 (Notebook Network Card)
Info regarding the losses sony makes :
Two years ago, when it was first released, the PS3 cost around $800 (£540) to make and retailed at just $600 (£400).
Two years on and the margins have significantly shrunk but, according to Business Week, the console is still losing money for Sony – around $50 (£35) per machine.
You can read more on the article here :
http://www.techradar.com/news/gaming/so ... old-497010