Unlike Sega and MS, Sony is an R&D hardware company. They make a lot of things. In designing up the PS2, they spent a lot of cash. Then they spent a hell of a lot more cash to build things like the chip foundries to produce the chips for the PS2.
In the end, before the first PS2 rolled off the production line for consumers, Sony had spent $2 billion! TWO BILLION!
Then we look at Sony's stock report for Oct-Dec 2000, and there is an interesting little blurb. It said that had Sony been able to meet demand with another 1 million PS2 units, they would have pocketed $175 million in profits. $175 million divided by one million consoles equals $175 per console profit.
Now, that is a bit high. This assumed that the average consumer continues to buy four games per console (so around $24 in royalties), and 2 accessories (about $30 in profit total). That reduces the $175 to about $120. Sony is making $120 profit per system.
[link|http://www.actsofgord.com/index.html|Acts of Gord] is an interesting site.